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Sialylated HEG1 has been reported as a highly specific and sensitive mesothelioma marker but a comprehensive evaluation of its expression in carcinomas in different organs, various sarcomas and reactive mesothelial proliferations has not been reported. The aim of this study was to evaluate the clinical applicability of HEG1 as a marker in the diagnosis of mesothelioma. HEG1 immunoreactivity was evaluated in whole sections of 122 mesotheliomas, 75 pulmonary carcinomas, 55 other carcinomas, 16 mesenchymal tumors, and 24 reactive mesothelial proliferations and in tissue microarrays containing 70 epithelioid (EM), 36 biphasic (BM), and 2 sarcomatoid mesotheliomas (SM). In whole sections and tissue microarrays, respectively, membranous HEG1 was expressed in 93.0% and 85.5% of EM, 81.3% and 69.4% of BM, 0% and 0% of SM. HEG1 was not expressed in pulmonary adenocarcinomas. HEG1 was expressed as cytoplasmic immunoreactivity in pulmonary squamous cell carcinomas (21.7%). Membranous HEG1 staining was seen in ovarian carcinomas (66.7%), thyroid carcinomas (100%), reactive conditions (16.7%), and mesenchymal tumors (18.8%). The sensitivity of membranous HEG1 expression to distinguish EM/BM from all carcinomas was 88.8%. The specificity for the differential diagnosis between EM/BM and all carcinomas and pulmonary carcinomas was 92.3% and 98.7%, respectively.

Context.— The accurate identification of different lung adenocarcinoma histologic subtypes is important for determining prognosis but can be challenging because of overlaps in the diagnostic features, leading to considerable interobserver variability. Objective.— To provide an overview of the diagnostic agreement for lung adenocarcinoma subtypes among pathologists and to create a ground truth using the clustering approach for downstream computational applications. Design.— Three sets of lung adenocarcinoma histologic images with different evaluation levels (small patches, areas with relatively uniform histology, and whole slide images) were reviewed by 18 international expert lung pathologists. Each image was classified into one or several lung adenocarcinoma subtypes. Results.— Among the 4702 patches of the first set, 1742 (37%) had an overall consensus among all pathologists. The overall Fleiss κ score for the agreement of all subtypes was 0.58. Using cluster analysis, pathologists were hierarchically grouped into 2 clusters, with κ scores of 0.588 and 0.563 in clusters 1 and 2, respectively. Similar results were obtained for the second and third sets, with fair-to-moderate agreements. Patches from the first 2 sets that obtained the consensus of the 18 pathologists were retrieved to form consensus patches and were regarded as the ground truth of lung adenocarcinoma subtypes. Conclusions.— Our observations highlight discrepancies among experts when assessing lung adenocarcinoma subtypes. However, a subsequent number of consensus patches could be retrieved from each cluster, which can be used as ground truth for the downstream computational pathology applications, with minimal influence from interobserver variability.

Malignant peritoneal mesothelioma historically carried a grim prognosis, but outcomes have improved substantially in recent decades. The prognostic significance of clinical, morphologic, and immunophenotypic features remains ill-defined. This multi-institutional cohort comprises 225 malignant peritoneal mesotheliomas, which were assessed for 21 clinical, morphologic, and immunohistochemical parameters. For epithelioid mesotheliomas, combining nuclear pleomorphism and mitotic index yielded a composite nuclear grade, using a previously standardized grading system. Correlation of clinical, morphologic, and immunohistochemical parameters with overall and disease-free survival was examined by univariate and multivariate analyses. On univariate analysis, longer overall survival was significantly associated with diagnosis after 2000 (P = 0.0001), age

Localized malignant mesotheliomas (LMM) is an uncommon and poorly recognized neoplasm. Its pathologic diagnosis is often surprising in patients with serosal/subserosal based localized tumors that are clinically suspicious for metastatic lesions or primary sarcomas. Once a tumor is diagnosed as "mesothelioma", LMM is often mistaken for diffuse malignant mesothelioma (DMM). Best currently available evidence about LMM was collected from the literature and cases diagnosed by members of the International Mesothelioma Panel (IMP). One hundred and one (101) LMM have been reported in the English literature. Patients had localized tumors with identical histopathologic features to DMM. Patients ranged in age from 6 to 82 years; 75% were men. Most (82%) of the tumors were intrathoracic. Others presented as intrahepatic, mesenteric, gastric, pancreatic, umbilical, splenic, and abdominal wall lesions. Tumors varied in size from 0.6 to 15 cm. Most patients underwent surgical resection and/or chemotherapy or radiation therapy. Median survival in a subset of patients was 29 months. Seventy two additional LMM from IMP institutions ranged in age from 28 to 95 years; 58.3% were men. Sixty tumors (83.3%) were intrathoracic, others presented in intraabdominal sites. Tumors varied in size from 1.2 to 19 cm. Median survival for 51 cases was 134 months. Best evidence was used to formulate guidelines for the diagnosis of LMM. It is important to distinguish LMM from DMM as their treatment and prognosis is different. A multidisciplinary approach is needed for the diagnosis of LMM as it shows identical histopathology and immunophenotype to DMM.

Pulmonary fibrosis is a progressive disease for which no curative treatment exists. We have previously engineered dermal fibroblasts to produce extracellular vesicles with tissue reparative properties dubbed activated specialized tissue effector extracellular vesicles (ASTEX). Here, we investigate the therapeutic utility of ASTEX in vitro and in a mouse model of bleomycin-induced lung injury. RNA sequencing demonstrates that ASTEX are enriched in micro-RNAs (miRs) cargo compared with EVs from untransduced dermal fibroblast EVs (DF-EVs). Treating primary macrophages with ASTEX reduced interleukin (IL)6 expression and increased IL10 expression compared with DF-EV-exposed macrophages. Furthermore, exposure of human lung fibroblasts or vascular endothelial cells to ASTEX reduced expression of smooth muscle actin, a hallmark of myofibroblast differentiation (respectively). In vivo, intratracheal administration of ASTEX in naïve healthy mice demonstrated a favorable safety profile with no changes in body weight, lung weight to body weight, fibrotic burden, or histological score 3 weeks postexposure. In an acute phase (short-term) bleomycin model of lung injury, ASTEX reduced lung weight to body weight, IL6 expression, and circulating monocytes. In a long-term setting, ASTEX improved survival and reduced fibrotic content in lung tissue. These results suggest potential immunomodulatory and antifibrotic properties of ASTEX in lung injury.

Diffuse malignant mesothelioma (MM) is an incurable tumour of the serosal membranes, which is often caused by exposure to asbestos and commonly diagnosed at advanced stage. Malignant mesothelioma in situ (MMIS) is now included as diagnostic category by the World Health Organization (WHO). However, our international survey of 34 pulmonary pathologists with an interest in MM diagnosis highlights inconsistency regarding how the diagnosis is being made by experts, despite published guidelines. Whilst the WHO restricts the diagnosis to surgical samples, the very concept has implication for cytological diagnosis, which is already regarded as controversial in itself by some. MMIS is currently only applicable as precursor to MM with an epithelioid component, and raises the possibility for different molecular pathways for different histological MM subtypes. The clinical implications of MMIS at this stage are uncertain, but aggressive therapies are being initiated in some instances. Based on the results of the survey we here present a critical appraisal of the concept, its clinical and conceptual implications and provide practice suggestions for diagnosis. A low threshold for ancillary testing is suggested. The designations of 'malignant mesothelioma, cannot exclude MMIS' or 'atypical mesothelial proliferation with molecular indicators of malignancy, so-called MMIS' could be used on cytology samples, adding 'no evidence of invasion in sample provided' for surgical samples. Clinical and radiological correlation are integral to diagnosis and best done at multidisciplinary meetings. Finally, collaborative studies are required to improve our understanding of MMIS. ispartof: PATHOLOGY vol:53 issue:4 pages:446-453 ispartof: location:England status: published

INTRODUCTION: Histologic subtypes of malignant pleural mesothelioma are a major prognostic indicator and decision denominator for all therapeutic strategies. In an ambiguous case, a rare transitional mesothelioma (TM) pattern may be diagnosed by pathologists either as epithelioid mesothelioma (EM), biphasic mesothelioma (BM), or sarcomatoid mesothelioma (SM). This study aimed to better characterize the TM subtype from a histological, immunohistochemical, and molecular standpoint. Deep learning of pathologic slides was applied to this cohort. METHODS: A random selection of 49 representative digitalized sections from surgical biopsies of TM was reviewed by 16 panelists. We evaluated BAP1 expression and CDKN2A (p16) homozygous deletion. We conducted a comprehensive, integrated, transcriptomic analysis. An unsupervised deep learning algorithm was trained to classify tumors. RESULTS: The 16 panelists recorded 784 diagnoses on the 49 cases. Even though a Kappa value of 0.42 is moderate, the presence of a TM component was diagnosed in 51%. In 49% of the histological evaluation, the reviewers classified the lesion as EM in 53%, SM in 33%, or BM in 14%. Median survival was 6.7 months. Loss of BAP1 observed in 44% was less frequent in TM than in EM and BM. p16 homozygous deletion was higher in TM (73%), followed by BM (63%) and SM (46%). RNA sequencing unsupervised clustering analysis revealed that TM grouped together and were closer to SM than to EM. Deep learning analysis achieved 94% accuracy for TM identification. CONCLUSION: These results revealed that the TM pattern should be classified as non-EM or at minimum as a subgroup of the SM type. ispartof: JOURNAL OF THORACIC ONCOLOGY vol:15 issue:6 pages:1037-1053 ispartof: location:United States status: published

INTRODUCTION: The 2015 WHO classification of tumors categorized malignant mesothelioma into epithelioid, biphasic (BMM), and sarcomatoid (SMM) for prognostic relevance and treatment decisions. The survival of BMM is suspected to correlate with the amount of the sarcomatoid component. The criteria for a sarcomatoid component and the interobserver variability between pathologists for identifying this component are not well described. In ambiguous cases, a “transitional” (TMM) subtype has been proposed but was not accepted as a specific subtype in the 2015 WHO classification. The aims of this study were to evaluate the interobserver agreement in the diagnosis of BMM, to determine the nature and the significance of TMM subtype, and to relate the percentage of sarcomatoid component with survival. The value of staining for BRCA-1-associated protein (BAP1) and CDKN2A(p16) fluorescence in situ hybridization (FISH) were also assessed with respect to each of the tumoral components. METHODS: The study was conducted by the International Mesothelioma Panel supported by the French National Cancer Institute, the network of rare cancer (EURACAN) and in collaboration with the International Association for the Study of Lung Cancer (IASLC). The patient cases include a random group of 42 surgical biopsy samples diagnosed as BMM with evaluation of SMM component by the French Panel of MESOPATH experts was selected from the total series of 971 BMM cases collected from 1998 to 2016. Fourteen international pathologists with expertise in mesothelioma reviewed digitally scanned slides (hematoxylin and eosin – stained and pan-cytokeratin) without knowledge of prior diagnosis or outcome. Cases with at least 7 of 14 pathologists recognizing TMM features were selected as a TMM group. Demographic, clinical, histopathologic, treatment, and follow-up data were retrieved from the MESOBANK database. BAP1 (clone C-4) loss and CDKN2A(p16) homozygous deletion (HD) were assessed by immunohistochemistry (IHC) and FISH, respectively. Kappa statistics were applied for interobserver agreement and multivariate analysis with Cox regression adjusted for age and gender was performed for survival analysis. RESULTS: The 14 panelists recorded a total of 544 diagnoses. The interobserver correlation was moderate (weighted Kappa = 0.45). Of the cases originally classified as BMM by MESOPATH, the reviewers agreed in 71% of cases (385 of 544 opinions), with cases classified as pure epithelioid in 17% (93 of 544), and pure sarcomatoid in 12% (66 of 544 opinions). Diagnosis of BMM was made on morphology or IHC alone in 23% of the cases and with additional assessment of IHC in 77% (402 of 544). The median overall survival (OS) of the 42 BMM cases was 8 months. The OS for BMM was significantly different from SMM and epithelioid malignant mesothelioma (p < 0.0001). In BMM, a sarcomatoid component of less than 80% correlated with a better survival (p = 0.02). There was a signicant difference in survival between BMM with TMM showing a median survival at 6 months compared to 12 months for those without TMM (p < 0.0001). BAP1 loss was observed in 50% (21 of 42) of the total cases and in both components in 26%. We also compared the TMM group to that of more aggressive patterns of epithelioid subtypes of mesothelioma (solid and pleomorphic of our large MESOPATH cohort). The curve of transitional type was persistently close to the OS curve of the sarcomatoid component. The group of sarcomatoid, transitional, and pleomorphic mesothelioma were very close to each other. We then considered the contribution of BAP1 immunostaining and loss of CDKN2A(p16) by FISH. BAP1 loss was observed in 50% (21 of 41) of the total cases and in both component in 27% of the cases (11 of 41). There was no significant difference in BAP1 loss between the TMM and non-TMM groups. HD CDKN2A(p16) was detected in 74% of the total cases with no significant difference between the TMM and non-TMM groups. In multivariate analysis, TMM morphology was an indicator of poor prognosis with a hazard ratio = 3.2; 95% confidence interval: 1.6 – 8.0; and p = 0.003 even when compared to the presence of HD CDKN2A(p16) on sarcomatoid component (hazard ratio = 4.5; 95% confidence interval: 1.2 – 16.3, p = 0.02). CONCLUSIONS: The interobserver concordance among the international mesothelioma and French mesothelioma panel suggests clinical utility for an updated definition of biphasic mesothelioma that allows better stratification of patients into risk groups for treatment decisions, systemic anticancer therapy, or selection for surgery or palliation. We also have shown the usefulness of FISH detection of CDKN2A(p16) HD compared to BAP1 loss on the spindle cell component for the separation in ambiguous cases between benign florid stromal reaction from true sarcomatoid component of biphasic mesothelioma. Taken together our results further validate the concept of transitional pattern as a poor prognostic indicator.

Malignant mesothelioma (MM) is an uncommon tumor that can be difficult to diagnose.- To provide updated, practical guidelines for the pathologic diagnosis of MM.- Pathologists involved in the International Mesothelioma Interest Group and others with an interest and expertise in the field contributed to this update. Reference material included up-to-date, peer-reviewed publications and textbooks.- There was discussion and consensus opinion regarding guidelines for (1) distinguishing benign from malignant mesothelial proliferations (both epithelioid and spindle cell lesions), (2) cytologic diagnosis of MM, (3) recognition of the key histologic features of pleural and peritoneal MM, (4) use of histochemical and immunohistochemical stains in the diagnosis and differential diagnosis of MM, (5) differentiating epithelioid MM from various carcinomas (lung, breast, ovarian, and colonic adenocarcinomas, and squamous cell and renal cell carcinomas), (6) diagnosis of sarcomatoid MM, (7) use of molecular markers in the diagnosis of MM, (8) electron microscopy in the diagnosis of MM, and (9) some caveats and pitfalls in the diagnosis of MM. Immunohistochemical panels are integral to the diagnosis of MM, but the exact makeup of panels employed is dependent on the differential diagnosis and on the antibodies available in a given laboratory. Depending on the morphology, immunohistochemical panels should contain both positive and negative markers for mesothelial differentiation and for lesions considered in the differential diagnosis. Immunohistochemical markers should have either sensitivity or specificity greater than 80% for the lesions in question. Interpretation of positivity generally should take into account the localization of the stain (eg, nuclear versus cytoplasmic) and the percentage of cells staining (10% is suggested for cytoplasmic and membranous markers). Selected molecular markers are now being used to distinguish benign from malignant mesothelial proliferations. These guidelines are meant to be a practical diagnostic reference for the pathologist; however, some new pathologic predictors of prognosis and response to therapy are also included.

Although Ki-67 labeling index (Ki-67%) is not a diagnostic or grading criterion in the World Health Organization classification of pulmonary carcinoid tumor, oncologists often request this test. A survey was administered at a North American Society for Neuroendocrine Tumors meeting to understand how Ki-67% is used in oncologic practices. A systematic literature review was performed to gather best evidence regarding the use of Ki-67%. Consecutive pulmonary carcinoids were stratified into pulmonary typical carcinoids with Ki-67%

Anaplastic thyroid carcinoma (ATC), one of the most aggressive subtypes of thyroid cancer, is composed of undifferentiated thyroid follicular cells demonstrating ultrastructural or immunohistochemical features of epithelial differentiation. Frequently, these tumors can be shown to have originated from papillary thyroid carcinoma (PTC). ATC exists on a morphologic spectrum composed of three main patterns: spindle cell (sarcomatoid), giant cell, and epithelial (squamous) components. Here we discuss two cases in which patients presented with upper airway symptoms and subsequently, a laryngotracheal lesion was detected by imaging studies and bronchoscopy. In each case, biopsies taken from these lesions showed invasive squamous cell carcinoma; however, both patients had previously undergone total thyroidectomy for PTC, and immunohistochemical studies revealed that the biopsied tumor cells were of thyroid origin. Furthermore, the cells harbored the BRAFV600E mutation, suggesting anaplastic transformation from PTC. Invasion into the larynx or trachea is a known complication of aggressive forms of thyroid cancer. However, laryngotracheal presentation of anaplastic thyroid carcinoma with squamous differentiation can easily be misdiagnosed as a primary squamous cell carcinoma. Immunohistochemical studies for thyroid lineage markers (e.g. PAX8) as well as squamous markers (e.g. p40, p63) should be performed, and if there is a known history of PTC, mutation analysis for BRAFV600E can support the diagnosis via molecular testing or immunohistochemistry.

Distinguishing between multiple lung primary tumors and intrapulmonary metastases is imperative for accurate staging. The American Joint Committee on Cancer (AJCC) criteria are routinely used for this purpose but can yield equivocal conclusions. This study evaluated whether next-generation sequencing (NGS) using the 50-gene AmpliSeq Cancer Hotspot Panel version 2 can help facilitate this distinction. NGS was performed on known primary-metastatic pairs (8 patients) and multiple lung adenocarcinomas (11 patients). Primary-metastatic pairs had high mutational concordance. Seven pairs shared mutations, and 1 was concordant for having no mutations. Driver mutations in KRAS (n = 4), EGFR (n = 2), and BRAF (n = 1) were always concordant. Multiple lung tumors from 3 patients were completely concordant and predicted by NGS to be intrapulmonary metastases, whereas 8 had completely discordant mutations and were predicted to be independent primary tumors. The NGS prediction correlated with the AJCC (eighth edition) prediction in all patients for whom the latter was unequivocal (8 of 11). Furthermore, it separated patients by overall survival. Patients with predicted multiple independent primary tumors by NGS had better survival than those with distant metastases (P = 0.016, log-rank test), whereas those with predicted intrapulmonary metastases had no difference (P = 0.527). With further validation, the 50-gene panel has the potential to serve as an adjunct to the AJCC criteria.

Context.— Tumor spread through alveolar spaces (STAS) has been correlated with unfavorable prognosis in lung adenocarcinomas treated with sublobar resection, but it is unknown whether STAS can be reliably identified in frozen section (FS) to help stratify patients for lobectomy or sublobar resection. Objective.— To evaluate STAS in FS. Design.— Tumor spread through alveolar spaces was evaluated in hematoxylin-eosin–stained FS, FS control slides, and all additional slides with lung tissue adjacent to tumor (AdLT) from 48 pT1–2 adenocarcinomas operated on using video-assisted thoracotomy (n = 25) or open thoracotomy (n = 23). The samples included lobectomies (n = 27) and sublobar resections (n = 21). The STAS incidences were compared by FS versus FS control versus AdLT, video-assisted thoracotomy versus open thoracotomy, and lobectomy versus sublobar resection. Sensitivity, specificity, and positive and negative predictive values of STAS+ findings were calculated. The literature was queried for best evidence regarding incidence and predictive value of STAS in FS. Results.— Tumor spread through alveolar spaces positivity was identified in 46 of 48 cases (95.8%), including 23 FS (47.9%), 32 FS control (66.7%), and 43 AdLT (89.6%). The STAS incidence was significantly higher in AdLT than in FS or FS control. Only 2 of the 25 cases that were STAS− in FS were true negatives. Frozen section sensitivity to detect STAS positivity was 50%, with a 100% positive predictive value and 8% negative predictive value. Systematic literature review identified no evidence regarding STAS identification in FS. Conclusions.— The sensitivity and negative predictive value of FS for STAS detection are unacceptably low. There are insufficient data to support intraoperative detection of STAS as a useful predictive feature to help stratify patients for lobectomy or sublobar resections.

Rationale: Fibrinolysis shutdown associated with severe thrombotic complications is a recently recognized syndrome that was previously seldom investigated in patients with severe severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection. It presents a unique therapeutic dilemma, as anticoagulation with heparin alone is insufficient to address the imbalance in fibrinolysis. And while the use of fibrinolytic agents could limit the disease severity, it is often associated with bleeding complications. There is a need for biomarkers that will guide the timely stratification of patients into those who may benefit from both anticoagulant and fibrinolytic therapies. Patient concerns: All 3 patients presented with shortness of breath along with comorbidities predisposing them to severe SARS-CoV-2 infection. One patient (Patient 3) also suffered from bilateral deep venous thrombosis. Diagnoses: All 3 patients tested positive for SARS-CoV-2 RNA by reverse transcription polymerase chain reaction (RT-PCR) and were eventually diagnosed with respiratory failure necessitating intubation. Interventions: All 3 patients required mechanical ventilation support, 2 of which also required renal replacement therapy. All 3 patients were also placed on anticoagulation therapy. Outcomes: In Patients 1 and 2, the initial D-dimer levels of 0.97 μg/ml fibrinogen equivalent units (FEU) and 0.83 μg/ml FEU were only slightly elevated (normal 20.0 μg/ml FEU, respectively, which dropped to 1.34 μg/ml FEU 8 days later in Patient 1 and to 2.94 μg/ml on hospital day 13 in Patient 2. In Patient 3, the D-dimer level on admission was found to be elevated to >20.00 μg/ml FEU together with imaging evidence of thrombosis. And although he received therapeutic heparin infusion, he still developed pulmonary embolism (PE) and his D-dimer level declined to 5.91 μg/ml FEU. Despite “improvement” in their D-dimer levels, all 3 patients succumbed to multi-system organ failure. On postmortem examination, numerous arterial and venous thromboses of varying ages, many consisting primarily of fibrin, were identified in the lungs of all patients. Lessons: High D-dimer levels, with subsequent downtrend correlating with clinical deterioration, seems to be an indicator of fibrinolysis suppression. These findings can help form a hypothesis, as larger cohorts are necessary to demonstrate their reproducibility.

The mediastinum can be the site of origin of a variety of benign and malignant tumors of peripheral nerve sheath origin. Although schwannoma is one of the most common tumors found in the posterior mediastinum, peripheral nerve sheath tumors are reported in all compartments of the mediastinum. The majority of peripheral nerve sheath tumors in the mediastinum as in other anatomic sites occur sporadically, and a subset of them, most notably neurofibromas, and to a lesser extent, schwannomas and malignant peripheral nerve sheath tumors, occur in patients with syndromes such as neurofibromatosis 1 (NF1). In this review, the characteristics of mediastinal nerve sheath tumors along with the histologic differential diagnosis are summarized. Primary emphasis is placed upon the use of morphologic criteria for establishing a definitive diagnosis with reference to photomicrographs to illustrate the classic and sometimes unusual features of this varied group of tumors. The judicious application of ancillary testing, most frequently immunohistochemistry, for separating peripheral nerve sheath tumors from each other and from their morphologic mimics is reviewed. Included in the review are the clinicopathologic features, clinical management and prognostic implications of benign and malignant mediastinal peripheral nerve sheath tumors.

Multiple tumor nodules are seen with increasing frequency in clinical practice. On the basis of the 2015 WHO classification of lung tumors, we assessed the reproducibility of the comprehensive histologic assessment to distinguish second primary lung cancers (SPLCs) from intrapulmonary metastases (IPMs), looking for the most distinctive histologic features. An international panel of lung pathologists reviewed a scanned sequential cohort of 126 tumors from 48 patients and recorded an agreed set of histologic features, including tumor typing and predominant pattern of adenocarcinoma, thereby opining whether the case was SPLC, IPM, or a combination thereof. Cohen κ statistics of 0.60 on overall assessment of SPLC or IPM indicated a good agreement. Likewise, there was good agreement (κ score 0.64, p < 0.0001) between WHO histologic pattern in individual cases and SPLC or IPM status, but the proportions diversified for histologic pattern and SPLC or IPM status (McNemar test, p < 0.0001). The strongest associations for distinguishing between SPLC and IPM were observed for nuclear pleomorphism, cell size, acinus formation, nucleolar size, mitotic rate, nuclear inclusions, intraalveolar clusters, and necrosis. Conversely, the associations for lymphocytosis, mucin content, lepidic growth, vascular invasion, macrophage response, clear cell change, acute inflammation keratinization, and emperipolesis did not reach significance with tumor extent. Comprehensive histologic assessment is recommended for distinguishing SPLC from IPM with good reproducibility among lung pathologists. In addition to main histologic type and predominant patterns of histologic subtypes, nuclear pleomorphism, cell size, acinus formation, nucleolar size, and mitotic rate strongly correlate with pathologic staging status.

ContextEvidence-based medicine has been proposed as a new paradigm for the identification and evaluation of medical information. Best available evidence or data are identified and used as the basis for the diagnosis and treatment of individual patients. Evidence-based pathology has adapted basic evidence-based medicine concepts to the specific needs of pathology and laboratory medicine.ObjectivesTo briefly review the history and basic concepts of evidence-based medicine and evidence-based pathology, describe how to perform and interpret systematic reviews, and discuss how to integrate best evidence into guidelines.Data SourcesPubMed (National Library of Medicine, Washington, DC) and Web of Science (Thompson Reuters, New York, New York) were used.ConclusionsEvidence-based pathology provides methodology to evaluate the quality of information published in pathology journals and apply it to the diagnosis of tissue samples and other tests from individual patients. Information is gathered through the use of systematic reviews, using a method that is less biased and more comprehensive than ad hoc literature searches. Published data are classified into evidence levels to provide readers with a quick impression about the quality and probable clinical validity of available information. Best available evidence is combined with personal experience for the formulation of evidence-based, rather than opinion-based, guidelines that address specific practice needs.

A recently described nuclear grading system predicted survival in patients with epithelioid malignant pleural mesothelioma. The current study was undertaken to validate the grading system and to identify additional prognostic factors. We analyzed cases of epithelioid malignant pleural mesothelioma from 17 institutions across the globe from 1998 to 2014. Nuclear grade was computed combining nuclear atypia and mitotic count into a grade of I-III using the published system. Nuclear grade was assessed by one pathologist for three institutions, the remaining were scored independently. The presence or absence of necrosis and predominant growth pattern were also evaluated. Two additional scoring systems were evaluated, one combining nuclear grade and necrosis and the other mitotic count and necrosis. Median overall survival was the primary endpoint. A total of 776 cases were identified including 301 (39%) nuclear grade I tumors, 354 (45%) grade II tumors and 121 (16%) grade III tumors. The overall survival was 16 months, and correlated independently with age (P=0.006), sex (0.015), necrosis (0.030), mitotic count (0.001), nuclear atypia (0.009), nuclear grade (

Distinguishing between multiple lung primary tumors and intrapulmonary metastases is imperative for accurate staging. The American Joint Committee on Cancer (AJCC) criteria are routinely used for this purpose but can yield equivocal conclusions. This study evaluated whether next-generation sequencing (NGS) using the 50-gene AmpliSeq Cancer Hotspot Panel version 2 can help facilitate this distinction. NGS was performed on known primary-metastatic pairs (8 patients) and multiple lung adenocarcinomas (11 patients). Primary-metastatic pairs had high mutational concordance. Seven pairs shared mutations, and 1 was concordant for having no mutations. Driver mutations in KRAS (n = 4), EGFR (n = 2), and BRAF (n = 1) were always concordant. Multiple lung tumors from 3 patients were completely concordant and predicted by NGS to be intrapulmonary metastases, whereas 8 had completely discordant mutations and were predicted to be independent primary tumors. The NGS prediction correlated with the AJCC (eighth edition) prediction in all patients for whom the latter was unequivocal (8 of 11). Furthermore, it separated patients by overall survival. Patients with predicted multiple independent primary tumors by NGS had better survival than those with distant metastases (P = 0.016, log-rank test), whereas those with predicted intrapulmonary metastases had no difference (P = 0.527). With further validation, the 50-gene panel has the potential to serve as an adjunct to the AJCC criteria.

Introduction The current WHO classification of lung cancer states that a diagnosis of SCLC can be reliably made on routine histological and cytological grounds but immunohistochemistry (IHC) may be required, particularly (1) in cases in which histologic features are equivocal and (2) in cases in which the pathologist wants to increase confidence in diagnosis. However, reproducibility studies based on hematoxylin and eosin–stained slides alone for SCLC versus large cell neuroendocrine carcinoma (LCNEC) have shown pairwise κ scores ranging from 0.35 to 0.81. This study examines whether judicious use of IHC improves diagnostic reproducibility for SCLC. Methods Nineteen lung pathologists studied interactive digital images of 79 tumors, predominantly neuroendocrine lung tumors. Images of resection and biopsy specimens were used to make diagnoses solely on the basis of morphologic features (level 1), morphologic features along with requested IHC staining results (level 2), and all available IHC staining results (level 3). Results For the 19 pathologists reading all 79 cases, the rate of agreement for level 1 was 64.7%, and it increased to 73.2% and 77.5% in levels 2 and 3, respectively. With IHC, κ scores for four tumor categories (SCLC, LCNEC, carcinoid tumors, and other) increased in resection samples from 0.43 to 0.60 and in biopsy specimens from 0.43 to 0.64. Conclusions Diagnosis using hematoxylin and eosin staining alone showeds moderate agreement among pathologists in tumors with neuroendocrine morphology, but agreement improved to good in most cases with the judicious use of IHC, especially in the diagnosis of SCLC. An approach for IHC in the differential diagnosis of SCLC is provided.

Context.—Frozen sections can help determine the extent of surgery by distinguishing in situ, minimally invasive, and invasive adenocarcinoma of the lung.Objective.—To evaluate our experience with the frozen section diagnosis of these lesions using root-cause analysis.Design.—Frozen sections from 224 consecutive primary pulmonary adenocarcinomas (in situ, 27 [12.1%]; minimally invasive, 46 [20.5%]; invasive, 151 [67.4%]) were reviewed. Features that could have contributed to frozen section errors and deferrals were evaluated.Results.—There were no false-positive diagnoses of malignancy. Frozen section errors and deferrals were identified in 12.1% (27 of 224) and 6.3% (14 of 224) of the cases, respectively. Significantly more errors occurred in the diagnosis of in situ and minimally invasive adenocarcinoma than in the diagnosis of invasive adenocarcinoma (P < .001). Frozen section errors and deferrals were twice as frequent in lesions smaller than 1.0 cm (P = .09). Features significantly associated with errors and deferrals included intraoperative consultation by more than one pathologist (P = .003) and more than one sample of frozen lung section (P = .001). Inflammation with reactive atypia, fibrosis/scar, sampling problems, and suboptimal quality sections were identified in 51.2% (21 of 41), 36.6% (15 of 41), 26.8% (11 of 41), and 9.8% (4 of 41) of the errors and deferrals, respectively (more than one of these factors was identified in some cases). Frozen section errors and deferrals had significant clinical impact in only 4 patients (1.8%); each had to undergo completion video-assisted thoracoscopic lobectomy less than 90 days after the initial surgery.Conclusions.—The distinction of in situ from minimally invasive adenocarcinoma is difficult in both frozen and permanent sections. We identified several technical and interpretive features that likely contributed to frozen section errors and deferrals and suggest practice modifications that are likely to improve diagnostic accuracy.

Neuroendocrine tumors (NETs) comprise a heterogeneous group of malignancies that arise from neuroendocrine cells throughout the body, most commonly originating from the lungs and gastrointestinal tract. Lung NETs can be classified as well differentiated (low-grade typical carcinoids [TCs] and intermediate-grade atypical carcinoids [ACs]) and poorly differentiated (high-grade large cell neuroendocrine carcinoma or SCLC). The incidence of these tumors is increasing, but disease awareness remains low among thoracic specialists, who are often involved in the diagnosis and early treatment for these patients. An accurate and timely diagnosis can ensure the implementation of appropriate treatment and have a substantial impact on prognosis. However, lung NET classification and diagnosis, particularly for TCs/ACs, are complicated by several factors, including a variable natural history and nonspecific symptoms. Surgery remains the only curative option for TCs/ACs, but there is a lack of consensus between lung NET management guidelines regarding optimal treatment approaches in the unresectable/metastatic setting on account of the limited availability of high-level clinical evidence. As a result, a multidisciplinary approach to management of lung NETs is required to ensure a consistent and optimal level of care. RADIANT-4 is the first phase III trial involving a large subpopulation of patients with advanced well-differentiated lung NETs to report reductions in the risk for disease progression and death with everolimus over placebo. This led to the recent U.S. approval of everolimus-the first agent approved for advanced lung TCs/ACs. To further improve evidence-based care, additional randomized controlled trials in patients with lung carcinoids are needed.

Objectives: To compare survival data in patients with resected bilateral synchronous pulmonary carcinomas with survival data from patients with lung cancer in pStages I through IV and to evaluate the usefulness of comprehensive histologic evaluation (CHE) of tumor histologic patterns to distinguish between synchronous primaries and intrapulmonary metastases. Methods: Ten-year overall survival (OS) data from 18 patients with 44 resected synchronous bilateral lung cancers, classified as “synchronous primaries” or “metastases” using CHE, were compared with survival data of 2,879 patients with lung cancer in pStages I through IV. Results: Forty and four tumors from 16 and two patients, respectively, were classified as synchronous primaries and metastases. There were no significant differences in survival between these 18 patients and pStage I controls or between the synchronous primaries and the metastases patient groups. However, there were significant differences in survival between the patients with resected synchronous bilateral tumors and each of the pStage II through IV control groups ( P < .05). Conclusions: Patients with resected synchronous bilateral lung cancers had similar 10-year OS to patients with stage I disease, regardless of CHE data. Most resected tumors were synchronous primaries by CHE.

The limited clinical success of anti‐HGF/MET drugs can be attributed to the lack of predictive biomarkers that adequately select patients for treatment. We demonstrate here that quantitative digital imaging of formalin fixed paraffin embedded tissues stained by immunohistochemistry can be used to measure signals from weakly staining antibodies and provides new opportunities to develop assays for detection of MET receptor activity. To establish a biomarker panel of MET activation, we employed seven antibodies measuring protein expression in the HGF/MET pathway in 20 cases and up to 80 cores from 18 human cancer types. The antibodies bind to epitopes in the extra (EC)‐ and intracellular (IC) domains of MET (MET4EC, SP44_METIC, D1C2_METIC), to MET‐pY1234/pY1235, a marker of MET kinase activation, as well as to HGF, pSFK or pMAPK. Expression of HGF was determined in tumour cells (T_HGF) as well as in stroma surrounding cancer (St_HGF). Remarkably, MET4EC correlated more strongly with pMET (r = 0.47) than SP44_METIC (r = 0.21) or D1C2_METIC (r = 0.08) across 18 cancer types. In addition, correlation coefficients of pMET and T_HGF (r = 0.38) and pMET and pSFK (r = 0.56) were high. Prediction models of MET activation reveal cancer‐type specific differences in performance of MET4EC, SP44_METIC and anti‐HGF antibodies. Thus, we conclude that assays to predict the response to HGF/MET inhibitors require a cancer‐type specific antibody selection and should be developed in those cancer types in which they are employed clinically.

The Use of Immunohistochemistry Improves the Diagnosis of SCLC. An International Reproducibility Study in a Demanding Set of Cases

Reproducibility of Comprehensive Histologic Assessment and Refining Histologic Criteria in P Staging of Multiple Tumor Nodules

Inflammatory bowel disease (IBD) is associated with a number of extraintestinal manifestations that may involve most organ systems. Extraintestinal manifestations are more common in Crohn disease (CD) and may include rheumatologic, ocular, dermatologic, biliary and pulmonary manifestations. The most common pulmonary manifestations of IBD are drug-induced lung disease. Other manifestations include parenchymal disease, pleuritis and overlap syndromes. We present a case series of 7 patients with non-infectious pulmonary manifestations of IBD, which included cryptogenic organizing pneumonia, usual interstitial pneumonitis (UIP), Langerhan's granulomatosis, and eosinophilic pneumonia. Concurrent extraintestinal manifestations present in these patients included arthralgia, iritis, and pyoderma gangrenosum. In most patients the development of pulmonary disease parallels that of the intestinal disease activity, extraintestinal manifestations and concurrent use of 5-ASA medications.

Patients with advanced pulmonary adenocarcinoma exhibiting overexpression or mutation of epidermal growth factor receptor tend to respond better to targeted therapy with tyrosine kinase inhibitors such as gefitinib and erlotinib. There is no consensus regarding how these neoplasms should be routinely tested for epidermal growth factor receptor (EGFR) and whether the results of immunohistochemistry (IHC), mutation analysis and fluorescent in situ hybridization correlate with each other or are independent predictive variables. We tested 100 pulmonary adenocarcinomas from patients with stage III or IV disease for EGFR abnormalities using IHC, PCR and fluorescent in situ hybridization (FISH) and compared the results using kappa and other statistical methods. The sensitivity of each test to detect an EGFR abnormality and its negative predictive value to estimate the presence of an abnormal test result by the other two methods were calculated. Abnormal EGFR test results were found in 62, 40 and 24% by IHC, FISH and PCR, respectively. kappa statistics yielded poor concordance between the results of the EGFR tests (kappa=0.3, and 0.2 for IHC and PCR and for PCR and FISH, respectively). Strong membranous immunoreactivity in more than 90% of the tumor cells was found to correlate with amplification or polysomy. PCR when used as a single test is likely to underestimate the presence of EGFR abnormalities that may significantly predict response to tyrosine kinase inhibitors. The need to standardize the approach to EGFR testing in patients with advanced pulmonary adenocarcinoma is discussed.

Context.—Tumor stage is the most important prognostic and predictive factor for patients with lung cancer, the most lethal neoplasm in the United States. It is used by thoracic surgeons, radiation therapists, and oncologists to determine whether patients with these neoplasms will be treated surgically with curative intent or with palliative radiation therapy and/or chemotherapy. Objective.—To review the variety of practical problems that can arise during the assessment of the pathologic stage and other prognostic/predictive factors included in the College of American Pathologist checklist for evaluation of resected lung neoplasms. Data Sources.—Potential practical difficulties that can arise during the pathologic staging of lung cancer patients include the distinction between pT1, pT2, and pT3 lesions based on their location and the presence of visceral pleura and/or parietal pleura invasion; the differential diagnosis between multiple synchronous or metachronous primary lung neoplasms (pT1m) and intrapulmonary metastasis of non-small cell carcinoma of the lung (pT4 or pM1 according to their location); and the role of the recent American Joint Committee on Cancer terminology for the classification of lymph nodes (isolated tumor cells, micrometastases, and metastases). Conclusions.—The variety of practical problems that can arise during the assessment of important prognostic and predictive features such as resection margin status and evaluation of lymphovascular invasion are reviewed. A brief discussion of the assessment of the effects of neoadjuvant therapy on resected lung neoplasms is also included.

Background Pulmonary nodules are frequently first diagnosed by frozen section, immediately followed by lobectomy or other procedures. The frozen section diagnosis of pulmonary nodules can be difficult, as inflammatory and fibrotic lesions can be confused for malignancy, creating intraoperative dilemmas for pathologists and thoracic surgeons. Methods We reviewed our experience at Cedars-Sinai Medical Center with the frozen section diagnoses of 183 consecutive pulmonary nodules smaller than 1.5 cm in diameter and calculated the sensitivity, specificity, and predictive values of this diagnostic procedure. Results One hundred and seventy four nodules were correctly classified by frozen section as neoplastic or nonneoplastic, six lesions were diagnosed equivocally, and two neoplasms were missed owing to sampling errors. The equivocal frozen section diagnoses included two bronchioloalveolar carcinomas (BAC) interpreted as "atypical hyperplasia, favor BAC," two BAC diagnosed as "alveolar hyperplasia," and two carcinoid tumors labeled as "atypical carcinoma" and "spindle cell lesion, carcinoid versus sclerosing hemangioma," respectively. The sensitivities for a diagnosis of neoplasia were 86.9% and 94.1% for nodules smaller than 1.1 cm in diameter and measuring 1.1 to 1.5 cm, respectively. The diagnostic accuracy of frozen sections was significantly better in nodules larger than 1.0 cm in diameter ( p = 0.05). There were no false-positive diagnoses of malignancy, resulting in 100% specificity. Conclusions Intraoperative consultation with frozen section is a sensitive and specific procedure for the diagnosis of malignancy from small pulmonary nodules. The distinction between BAC and atypical adenomatous hyperplasia, and of small peripheral carcinoid tumors from other lesions, can be difficult by frozen section. Thoracic surgeons need to become aware of these problems and develop appropriate therapeutic strategies.

The classification of small cell lung cancer (SCLC) and non-small cell lung cancer (NSCLC) can pose diagnostic problems due to inter-observer variability and other limitations of histopathology. There is an interest in developing classificatory models of lung neoplasms based on the analysis of multivariate molecular data with statistical methods and/or neural networks. DNA methylation levels at 20 loci were measured in 41 SCLC and 46 NSCLC cell lines with the quantitative real-time PCR method MethyLight. The data were analyzed with artificial neural networks (ANN) and linear discriminant analysis (LDA) to classify the cell lines into SCLC or into NSCLC. Models used either data from all 20 loci, or from five significant DNA methylation loci that were selected by a step-wise back-propagation procedure (PTGS2, CALCA, MTHFR, ESR1, and CDKN2A). The data were sorted randomly by cell line into 10 different data sets, each with training and testing subsets composed of 71 and 16 of the cases, respectively. Ten ANN models were trained using the 10 data sets: five using 20 variables, and five using the five variables selected by step-wise back-propagation. The ANN models with 20 input variables correctly classified 100% of the cell lines, while the models with only five variables correctly classified 87 to 100% of cases. For comparison, 10 different LDA models were trained and tested using the same data sets with either the original data or with logarithmically transformed data. Again, half of the models used all 20 variables while the others used only the five significant variables. LDA models provided correct classifications in 62.5% to 87.5% of cases. The classifications provided by all of the different models were compared with kappa statistics, yielding kappa values ranging from 0.25 to 1.0. We conclude that ANN models based on DNA methylation profiles can objectively classify SCLC and NSCLC cells lines with substantial to perfect concordance, while LDA models based on DNA methylation profiles provide poor to substantial concordance. Our work supports the promise of ANN analysis of DNA methylation data as a powerful approach for the development of automated methods for lung cancer classification.

Background . Assessment of surgical risk in patients undergoing pulmonary resection is a fundamental goal for thoracic surgeons. Usually used risk indices do not predict the individual outcome. Neural networks (NN) are artificial intelligence software models that have been used for estimation of several prognostic situations. Methods . Ninety-six clinical and laboratory features from each one of 141 patients who underwent lung resection were retrospectively collected. The variables were used as input data for the software. Cases were divided into a training set (n = 113) and a test set (n = 28). Four NN models were trained using the data from the training set: (1) using all variables; (2) using only the Goldman and Torrington scores; (3) using all variables except for the two scores. A fourth NN was programmed with all variables to estimate the development of major postoperative complications. The trained NN models were tested with the test set data. Results . The NN using all variables with or without the scores were able to correctly classify all 28 test cases against actual outcome. The NN using all variables also estimated major postoperative complications correctly in all 28 test cases. The NN using only two indices (Goldman and Torrington) yielded 6 of 28 errors in classification. Conclusions . These data suggest that NN can integrate results from multiple data predicting the individual outcome for patients, rather than assigning them to less-precise risk group categories.

Context.—Health care providers have expressed increasing interest in incorporating digital images of gross pathology specimens and photomicrographs in routine pathology reports. Objective.—To describe the multiple technical and logistical challenges involved in the integration of the various components needed for the development of a system for integrated Web-based viewing, storage, and distribution of digital images in a large health system. Design.—An Oracle version 8.1.6 database was developed to store, index, and deploy pathology digital photographs via our Intranet. The database allows for retrieval of images by patient demographics or by SNOMED code information. Setting.—The Intranet of a large health system accessible from multiple computers located within the medical center and at distant private physician offices. Results.—The images can be viewed using any of the workstations of the health system that have authorized access to our Intranet, using a standard browser or a browser configured with an external viewer or inexpensive plug-in software, such as Prizm 2.0. The images can be printed on paper or transferred to film using a digital film recorder. Digital images can also be displayed at pathology conferences by using wireless local area network (LAN) and secure remote technologies. Conclusions.—The standardization of technologies and the adoption of a Web interface for all our computer systems allows us to distribute digital images from a pathology database to a potentially large group of users distributed in multiple locations throughout a large medical center.

We morphometrically evaluated 5-micron HE-stained sections from 28 surgically resected high-grade pulmonary neuroendocrine neoplasms, including 16 small cell lung carcinomas (SCLCs) and 12 large cell neuroendocrine carcinomas (LCNECs). For each case, 200 tumor nuclei and 20 to 100 normal lymphocytes were measured. The frequency distributions of tumor cell/lymphocyte (TC/L) size ratios were plotted in bins ranging from 1 to 6, classified into 6 histogram types with TC/L size ratio peaks ranging from 2 to 6 (A-E) and a histogram with a wide distribution (F). SCLCs fit histograms A through E; LCNECs, A through F. Morphometry demonstrated considerable nuclear size overlap in high-grade neoplasms. Approximately one third of SCLCs exhibited considerable numbers of neoplastic cells that were larger than 3 normal lymphocytes, while 4 of 12 LCNECs had a predominant number of small cells. Ten tumors exhibited a B histogram with a "borderline" peak TC/L of 3. The rule that a TC/L size ratio larger than 3 helps distinguish "large" from "small" neoplastic cells was confirmed in only 9 of 28 cases. The use of more generic terminology such as "high-grade neuroendocrine carcinoma" or "grade III neuroendocrine carcinoma" for SCLC and LCNEC is discussed.

Telepathology (TP) is the practice of pathology at a distance using videomicroscopy and telecommunication tools. We explore the use of "virtual microscopy" techniques and the Internet as tools for TP gastrointestinal biopsy consultations. Thirty-five gastrointestinal biopsy specimens were photographed in Los Angeles by using a high-resolution digital camera, a light microscope, and a Pentium 166 microcomputer. Several (2-8) digital photomicrographs were collected at 40x or 100x optical magnification, using 2,700 x 3,400 pixel resolution. The photomicrographs illustrated all the tissue fragments present in 1 of the biopsy levels. They were saved in medium compression JPEG image format. These images can be magnified digitally up to 600% without visible degradation and scrolled at different magnifications on a video monitor, simulating examination under a light microscope. The images files (281 to 3,324 KB) were attached to e-mail messages containing patient information and sent through the Internet to Michigan for interpretation using a Power Macintosh 7100 system. The e-mail process was successful in 100% of instances; 2 files were corrupted owing to user error and had to be resent. Additional photos were requested in 1 case. In 33 of 35 cases, there was diagnostic concordance between the original and the TP diagnoses. The 2 discrepancies were due to diagnostic disagreement. This technology offers pathologists relatively inexpensive and effective tools for gastrointestinal TP consultations.

Liver cell dysplasia (LCD) is considered a preneoplastic lesion, whose characterization and differentiation from hepatocellular carcinoma (HCC) and from the reactive changes seen in cirrhosis has been controversial. We studied 12 cases of LCD (large cell type) with image analysis techniques (IA) and compared the findings with those of HCC (n = 40), and a spectrum of non-neoplastic hepatic lesions including normal liver and cirrhosis (n = 49). A minimum of 200 Feulgen-stained nuclei were measured from each lesion with the CAS 200 image analysis system. The data were collected with the aid of CellSheet software. Thirty-four variables were measured, including geometric, textural, and photometric nuclear features and DNA ploidy. The data were analyzed with multivariate statistics and a backpropagation neural network (NN). Stepwise statistical analysis selected 22 variables that were statistically significant in the three groups with P values

DNA "ploidy" histogram interpretation is one of the most important sources of variation in DNA image cytometry and is influenced by multiple technical factors such as scaling, selection of peaks, and variable classification criteria. A rule-based expert system was developed to automate and eliminate subjectivity from this interpretative process. Ninety-eight Feulgen stained histologic sections from patients with breast, colon, and lung cancer were measured with the CAS 200 image analysis system (Becton Dickinson, Santa Clara, CA); they included diploid (n = 42), aneuploid (n = 46), tetraploid (n = 7), and multiploid (n = 3) examples. The data was converted from listmode format into ASCII with the aid of CELLSHEET software (JVC Imaging, Elmhurst, IL). Individual microphotometric nuclear measurements were sorted to one of 64 bins based on DNA index. The 64 bins were then divided into 5 semi-arbitrarily defined ranges: hypodiploid, diploid, aneuploid, tetraploid, and hypertetraploid. The nuclear percentages in each range were calculated with EXCEL 4.0 (Microsoft, Redmond, WA). The histograms were divided into 2 equal sets: training and testing. The data from the training set were used to develop 16 IF-THEN rules to classify the histograms into diploid, aneuploid, or tetraploid. A macro was programmed in EXCEL to automate all these operations. The rule-based expert system classified correctly 45/50 histograms of the training set. Two tetraploid histograms were classified as aneuploid. Three multiploid histograms were classified as tetraploid. All histograms in the testing set were correctly classified by the expert system. The potential role of rule-based expert system technology for the objective classification of DNA "ploidy" histograms measured by image cytometry is discussed.

This case report describes the rare occurrence of a T790M resistance mutation found in a central nervous system (CNS) parenchymal metastasis. A concomitant squamous histology transformation in a lung non-T790M-resistant metastasis is also described. The authors hypothesize that this CNS resistance and histology transformation may have resulted from intermittent use of erlotinib treatment. This case report emphasizes the complexities of using erlotinib in the induction setting.

The efficacy of CTLA4Ig in blocking immune activation and allograft rejection (AR) was tested in an aggressive and rapid model of rat lung AR (Brown Norway [BN]→Lewis [LEW]). CTLA4Ig is a recombinant soluble protein that binds with high affinity to rat B7/BB1 and other surface molecules on APCs, subsequently blocking the binding of B7/BB1 to CD28/CTLA4 on T cells. This interrupts the costimulatory pathway critical for complete T cell activation and completion of the AR process. Left single-lung transplants were performed between BN→Lew. Five allograft recipients were examined in each group. At transplantation, animals received 250 μg of CTLA4Ig or 250 μg of control Ig intraperitoneally daily until sacrifice. Animals were sacrificed on days 2, 4, and 7 after transplant. Control (BN→Lew) grafts show irreversible rejection by day 7. Syngeneic (Lew→Lew) grafts show no AR on day 7. AR episodes were graded histologically (stages 0-IV and pathologic intensity of inflammation was graded on percentage of involvement. Cytokine transcript levels were measured in control and CTLA4Ig-treated animals (n=5 in each group) on day 7 using reverse transcriptase polymerase chain reaction techniques. The most profound differences were found on day 7 after transplant. The degree of lymphocytic infiltration was greater in the CTLA4Ig group (perivascular: 4±0 vs. 2.6±0.6, peribronchial: 4±0 vs. 2.2±0.4, and peribronchiolar: 3.6±0.5 vs. 2±0.3, P

Malignant mesothelioma (MM) is an uncommon tumor that can be difficult to diagnose.To provide updated practical guidelines for the pathologic diagnosis of MM.Pathologists involved in the International Mesothelioma Interest Group and others with an interest in the field contributed to this update. Reference material includes peer-reviewed publications and textbooks.There was consensus opinion regarding (1) distinction of benign from malignant mesothelial proliferations (both epithelioid and spindle cell lesions), (2) cytologic diagnosis of MM, (3) key histologic features of pleural and peritoneal MM, (4) use of histochemical and immunohistochemical stains in the diagnosis and differential diagnosis of MM, (5) differentiation of epithelioid MM from various carcinomas (lung, breast, ovarian, and colonic adenocarcinomas, and squamous cell and renal cell carcinomas), (6) diagnosis of sarcomatoid mesothelioma, (7) use of molecular markers in the diagnosis of MM, (8) electron microscopy in the diagnosis of MM, and (9) some caveats and pitfalls in the diagnosis of MM. Immunohistochemical panels are integral to the diagnosis of MM, but the exact makeup of panels used is dependent on the differential diagnosis and on the antibodies available in a given laboratory. Immunohistochemical panels should contain both positive and negative markers. It is recommended that immunohistochemical markers have either sensitivity or specificity greater than 80% for the lesions in question. Interpretation of positivity generally should take into account the localization of the stain (eg, nuclear versus cytoplasmic) and the percentage of cells staining (10% is suggested for cytoplasmic membranous markers). These guidelines are meant to be a practical reference for the pathologist.

Pulmonary carcinoid tumors are currently classified as typical or atypical based on the mitotic index (2 per 10 hpf) and/or the presence of necrosis. Following incorporation of the Ki-67 index into the classification of GI carcinoid tumors, our oncologists have also been requesting this test as part of the work-up of pulmonary carcinoid tumors although there are currently no established criteria for interpreting Ki-67 index in these neoplasms. We utilized the Ariol® SL50 Image Analyzer system to measure the Ki-67 index in 101 pulmonary carcinoid tumors (78 typical and 23 atypical) and then correlated the Ki-67 index and the histological diagnoses in univariate and multivariable analysis with overall survival. The mean Ki-67 indices for the typical carcinoids (3.7 s.d.±4.0) and the atypical carcinoids (18.8 s.d.±17.1) were significantly different (P

Context.—Contrary to the intuitive impressions of many pathologists, several areas exist in laboratory medicine where evidence-based medicine (EBM) principles are not applied. These include aspects of both anatomic and clinical pathology. Some non-EBM practices are perpetuated by clinical “consumers” of laboratory services because of inadequate education, habit, or overreliance on empirical factors. Other faulty procedures are driven by pathologists themselves.Objectives.—To consider (1) several selected problem areas representing non-EBM practices in laboratory medicine; such examples include ideas and techniques that concern metastatic malignancies, “targeted” oncologic therapy, general laboratory testing and data utilization, evaluation of selected coagulation defects, administration of blood products, and analysis of hepatic iron-overload syndromes; and (2) EBM principles as methods for remediation of deficiencies in hospital pathology, and implements for the construction of “quality” practices in our specialty.Data Sources.—Current English literature relating to evidence-based principles in pathology and laboratory medicine, as well as the authors' experience.Conclusions.—Evidence-based medicine holds the promise of optimizing laboratory services to produce “quality” practices in pathology. It will also be a key to restraining the overall cost of health care.

The distinction between primary lung adenocarcinoma and metastatic breast carcinoma in patients with a history of breast cancer is difficult by frozen section (FS) analysis. Our experience with 129 FSs from 121 patients with a pulmonary nodule and a history of breast cancer was reviewed. The pretest odds ratio of primary pulmonary carcinoma/metastatic breast carcinoma was 2.6. The incidence of 12 histopathologic features was assessed in a “training set” composed of 20 FSs, 10 with primary lung adenocarcinoma and 10 with metastatic breast cancer. A differential diagnosis model composed of significant pathologic features that favor the diagnosis of primary lung adenocarcinoma (acini, lepidic growth, nuclear pseudoinclusions, and scar) or metastatic breast carcinoma (comedonecrosis, solid nests, trabecular architecture, and cribriform growth) was identified. The external validity of this model was successfully tested by challenging 19 pathologists and trainees with a test set of 20 unknown FSs, supporting the clinical applicability of the diagnostic model.

Context.—The mechanism of fibrosis is not clear in patients with obliterative bronchiolitis after a remote injury. Immune-mediated progression may be a reason. c-KIT (CD117)–positive mast cells have been associated with chronic fibrosing diseases and may potentially be treated with imatinib (Gleevec), a c-KIT blocker.Objective.—To evaluate the role of mast cells in fibrosis associated with obliterative bronchiolitis.Design.—Four cases of obliterative bronchiolitis (household cleaner exposure, ammonia exposure, idiopathic, and posttransplantation) were compared with asthma/emphysema. Small and large airways were stained for CD20, CD3, CD4, CD8, CD117, CD34, CD25, stem cell factor (c-KIT ligand) and with toluidine blue, hematoxylin-eosin, and trichrome. c-KIT (CD117)–stained slides were digitally scanned with Aperio ScanScope and stained cells within the epithelium and subepithelium of small and large airways were counted (per millimeter of basement membrane).Results.—Mast cells were concentrated within the involved subepithelium of small airways in obliterative bronchiolitis (122 cells/mm), unlike asthma/emphysema (25 cells/mm). Conversely, there were more mast cells in the epithelium in cases of asthma/emphysema than in obliterative bronchiolitis (7 cells/mm and 2 cells/mm, respectively). Mast cells were significantly increased around involved airways versus uninvolved airways (52 cells/mm vs 14 cells/mm). Large airways in either group had similar c-KIT (CD117) expression. Stem cell factor was not increased.Conclusions.—Mast cells appear to be concentrated in the lesional small-airway subepithelium in obliterative bronchiolitis. The possible role of c-KIT inhibitors such as imatinib (Gleevec) in the progression of fibrosis preceding the development of obliterative bronchiolitis is discussed.

The frozen section diagnosis of lung nodules is difficult because inflammatory atypia and histologic artifacts can simulate a malignancy. From a total of 2,405 frozen sections examined, 143 cases were misdiagnosed or deferred, including 65 with reactive atypia (RA) and 35 bronchioloalveolar carcinomas or well-differentiated adenocarcinomas (BAC-AC), resulting in deferral and error rates of 4.36% and 1.58%, respectively. The presence of 25 pathologic features was evaluated by using an evidence-based pathology (EBP) approach. Of the pathologic features, 11 were significant at a P value of less than .05 but exhibited variable incidence in AC and RA. Positive likelihood ratios allowed for identification of the 5 most useful pathologic features for the diagnosis of AC: multiple growth patterns, anisocytosis, atypia more than 75%, macronucleoli, and atypical mitoses. Granulomas favored the diagnosis of RA. An EBP approach is helpful to stratify pathologic features according to their clinical applicability.