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ObjectivesPromotion of high-quality care at a lower cost requires educational initiatives across the continuum of medical education. A needs assessment was performed to inform the design of an educational tool with the goal of teaching laboratory stewardship to medical students.MethodsThe needs assessment consisted of semistructured interviews with core clerkship directors and residency program directors at our institution, a national survey to the Undergraduate Medical Educators Section (UMEDS) of the Association of Pathology Chairs, and a review of existing online resources that teach high-value care.ResultsTwo major themes emerged regarding opportunities to enhance laboratory stewardship education: appropriate ordering (knowledge of test indications, pretest/posttest probability, appropriateness criteria, recognition of unnecessary testing) and correct interpretation (understanding test specifications, factors that affect the test result, recognizing inaccurate results).ConclusionsThe online educational tool will focus on the curricular needs identified, using a multidisciplinary approach for development and implementation.

Emotional intelligence (EI) is the ability to recognize, understand, and manage emotions in yourself and in others. EI has long been recognized as a critical component for individual and organizational success within the business realm, and there is emerging evidence that enhancing EI is equally important in the medical setting. EI can improve interpersonal communications, enable constructive conflict resolution, and promote a culture of professionalism. As healthcare becomes increasingly team-based, proficiency in EI will be required to build consensus among multidisciplinary stakeholders, and effect change in attitudes and behaviors that result in improved patient safety and clinical outcomes. Based on the existing literature and the authors' experiences, these 12 tips provide practical suggestions on how to introduce EI into a medical curriculum. These tips have broad applicability, and can be implemented in courses on topics such as professionalism, leadership development, empathy, patient safety, or wellness.

Context.— Current health care spending is unsustainable, and there is a need to teach high-value care principles to future physicians. Pathology-Teaches is an educational intervention designed to teach laboratory stewardship early in clinical training, at the level of the medical student in their core clinical clerkships. Objective.— To assess the pilot implementation of case-based educational modules in 5 required core clerkships at our institution. Design.— The online cases were developed by using a multidisciplinary approach. In the Pathology-Teaches educational module, students make decisions regarding the ordering or interpretation of laboratory testing within the context of a clinical scenario and receive immediate feedback during the case. The intervention was assessed by using pretest and posttest. Student feedback was also collected from end-of-rotation evaluations. Results.— A total of 203 students completed the Pathology-Teaches pilot, including 72 in Family Medicine, 72 in Emergency Medicine, 24 in Internal Medicine, 24 in Neurology, and 11 in Obstetrics-Gynecology (OB-GYN). Pathology-Teaches utility was demonstrated by significantly increased improvement between pretest and posttest scores (mean, 63.1% versus 83.5%; P < .001; Hedge g effect size = 0.93). Of the 494 students who completed the Pathology-Teaches questions on the end-of-rotation evaluation, 251 provided specific feedback, with 38.6% (97 of 251) rating the activity as “extremely valuable” or “very valuable,” and 41.4% (104 of 251) as “some/moderate value.” Qualitative feedback included 17 positive comments with 6 requests to scale up or include more cases, 16 constructive comments for improvement mainly regarding the technical aspects, and 5 negative comments. Conclusions.— Pathology-Teaches effectively teaches stewardship concepts, and most students perceived value in this educational intervention.

Pediatric-type nodal follicular lymphoma (PTNFL) is a variant of follicular lymphoma (FL) characterized by limited-stage presentation and invariably benign behavior despite often high-grade histological appearance. It is important to distinguish PTNFL from typical FL in order to avoid unnecessary treatment; however, this distinction relies solely on clinical and pathological criteria, which may be variably applied. To define the genetic landscape of PTNFL, we performed copy number analysis and exome and/or targeted sequencing of 26 PTNFLs (16 pediatric and 10 adult). The most commonly mutated gene in PTNFL was MAP2K1, encoding MEK1, with a mutation frequency of 43%. All MAP2K1 mutations were activating missense mutations localized to exons 2 and 3, which encode negative regulatory and catalytic domains, respectively. Missense mutations in MAPK1 (2/22) and RRAS (1/22) were identified in cases that lacked MAP2K1 mutations. The second most commonly mutated gene in PTNFL was TNFRSF14, with a mutation frequency of 29%, similar to that seen in limited-stage typical FL (P = .35). PTNFL was otherwise genomically bland and specifically lacked recurrent mutations in epigenetic modifiers (eg, CREBBP, KMT2D). Copy number aberrations affected a mean of only 0.5% of PTNFL genomes, compared with 10% of limited-stage typical FL genomes (P < .02). Importantly, the mutational profiles of PTNFLs in children and adults were highly similar. Together, these findings define PTNFL as a biologically and clinically distinct indolent lymphoma of children and adults characterized by a high prevalence of MAPK pathway mutations and a near absence of mutations in epigenetic modifiers.

Background CD49d is emerging as a powerful adverse prognostic marker in chronic lymphocytic leukemia/small lymphocytic lymphoma (CLL/SLL). However, flow cytometric testing for CD49d has not yet been widely adopted in the United States, in part due to the lack of establishment of its performance characteristics in the clinical setting, especially in comparison with the more common CLL/SLL prognostic markers CD38 and ZAP-70. Methods CD49d expression levels in 124 CLL/SLL cases were assessed among peripheral blood (PB), bone marrow (BM), and lymph node (LN) specimens and correlated with available CD38 and ZAP-70 expression and cytogenetic findings. For 10 PB/BM specimens, the stability of CD49d, CD38, and ZAP-70 expression was assessed at

Primary mediastinal large B-cell lymphoma (PMBL) is a mature large B-cell lymphoma of putative thymic B-cell origin involving the mediastinum with younger age distribution and better prognosis than diffuse large B-cell lymphoma (DLBCL), not otherwise specified. Recently, based on gene expression profile analysis and morphologic findings, cases of PMBL without mediastinal involvement have been reported. In this study, we analyzed 3 cases of nodal DLBCL with morphologic features of PMBL presenting in submandibular or supraclavicular lymph nodes, in middle-aged to elderly patients, 2 of them without clinical or radiologic evidence of mediastinal involvement. The 3 patients presented with stage I/II disease and had excellent response to R-CHOP/R-EPOCH therapy. The 3 cases showed MAL expression and were positive for CD23 and/or CD30. All 3 cases expressed cyclin D1 with copy number gains of CCND1 gene but without rearrangement. There was no rearrangement of CIITA or PDL1/PDL2. Reverse transcriptase-multiplex ligation-dependent probe amplification, a mRNA-based gene expression profile analysis revealed high probability of PMBL (87.6%, 98.7%, and 99%) in these 3 cases. Targeted next-generation sequencing analysis showed SOCS1 mutations in the 3 cases, and TNFAIP3 and XPO1 mutations in one, further supporting the diagnosis of PMBL. In conclusion, we report 3 cases of nodal PMBL, 2 of them without mediastinal mass, and expression of cyclin D1 due to copy number gains of CCND1 gene, a diagnostic pitfall with mantle cell lymphoma and DLBCL, not otherwise specified.

Lyme disease can affect the central nervous system causing a B-cell-predominant lymphocytic pleocytosis. Since most reactions to infection in the cerebrospinal fluid (CSF) are typically T-cell predominant, a B-cell-predominant lymphocytosis raises concern for lymphoma. We present 3 Lyme neuroborreliosis cases in order to illustrate the challenging cytomorphological and immunophenotypic features of their CSF specimens. Three male patients who presented with central nervous system manifestations were diagnosed with Lyme disease. The clinical presentation, laboratory tests, CSF cytological examination and flow-cytometric studies were described for each case. CSF cytology showed lymphocytic pleocytosis with increased plasmacytoid cells and/or plasma cells. Flow cytometry showed the presence of polytypic B lymphocytes with evidence of plasmacytic differentiation in 2 cases. In all cases, Lyme disease was confirmed by the Lyme screening test and Western blotting. In such cases of Lyme neuroborreliosis, flow cytometry of CSF samples employing plasmacytic markers and cytoplasmic light-chain analysis is diagnostically helpful to exclude lymphoma.

[Figure][1] A 62-year-old man presented with headache, dysarthria, and a right subdural hematoma. Laboratory studies were remarkable for leukocytosis (white blood cells, 29.4 × 109/L), thrombocytopenia (platelets, 87 × 109/L), and anemia (hemoglobin, 7.8 g/dL) without rouleaux. Many

AimsElimination of non-value added testing without compromising high-quality clinical care is an important mandate for laboratories in a value-based reimbursement system. The goal of this study was to determine the optimal combination of flow cytometric markers for a screening approach that balances efficiency and accuracy.MethodsAn audit over 9 months of flow cytometric testing was performed, including rereview of all dot plots from positive cases.ResultsOf the 807 cases in which leukaemia/lymphoma testing was performed, 23 were non-diagnostic and 189 represented bronchoalveolar lavage specimens. Of the remaining 595 cases, 137 (23%) were positive for an abnormal haematolymphoid population. Review of the positive cases identified minimum requirements for a screening tube as well as analysis strategies to overcome the diagnostic pitfalls noted. It is estimated that 38% fewer antibodies would be used in a screening approach, representing an opportunity for significant cost savings.ConclusionsWe provide a framework for developing an evidence-based screening combination for cost-effective characterisation of haematolymphoid malignancies, promoting adoption of ‘just-in-time’ testing systems that tailor the evaluation to the diagnostic need.

Acute myeloid leukemia arising from chronic myelomonocytic leukemia is currently classified as acute myeloid leukemia with myelodysplasia-related changes, a high-risk subtype. However, the specific features of these cases have not been well described. We studied 38 patients with chronic myelomonocytic leukemia who progressed to acute myeloid leukemia. We compared the clinicopathologic and genetic features of these cases with 180 patients with de novo acute myeloid leukemia and 34 patients with acute myeloid leukemia following myelodysplastic syndromes. We also examined features associated with progression from chronic myelomonocytic leukemia to acute myeloid leukemia by comparing the progressed chronic myelomonocytic leukemia cases with a cohort of chronic myelomonocytic leukemia cases that did not transform to acute myeloid leukemia. Higher white blood cell count, marrow cellularity, karyotype risk score, and Revised International Prognostic Scoring System score were associated with more rapid progression from chronic myelomonocytic leukemia to acute myeloid leukemia. Patients with acute myeloid leukemia ex chronic myelomonocytic leukemia were older (P

Background: T-cell immunoglobulin mucin-3 (TIM3) has recently been described as an acute myeloid leukemia (AML) stem cell antigen expressed on leukemic myeloblasts, but not on normal hematopoietic stem cells. TIM3 is also expressed by monocytes, natural killer cells, and several T cell subsets; however, normal myeloblasts have not been well-characterized or compared to AML. A specific flow cytometric marker capable of separating leukemic myeloblasts from non-neoplastic myeloblasts would be diagnostically useful, especially in the post-chemotherapy setting. Methods: TIM3 myeloblast expression was assessed in 69 bone marrow and/or peripheral blood specimens, including 27 AML and 42 non-neoplastic cases (20 with a recent history of chemotherapy). TIM3 median fluorescence intensity (MFI) was evaluated within myeloblast, monocyte, T cell, and natural killer cell populations. Results: The median percentage of myeloblasts positive for TIM3 was lower in non-neoplastic specimens without a history of recent chemotherapy (50.3%) as compared to AML (71.4%), but not significantly different as compared to non-leukemic myeloblasts in the post-chemotherapy setting (72.4%). Mean myeloblast TIM3 MFI was higher in AML myeloblasts and non-leukemic myeloblasts in the post-chemotherapy setting as compared to non-neoplastic myeloblasts in cases lacking a history of chemotherapy. Mean monocyte, natural killer cell, and T-cell TIM3 MFI remained relatively constant in varied clinical settings. Conclusions: We confirm that leukemic myeloblasts overexpress TIM3 as compared to non-neoplastic controls; however, high levels of expression may also be seen among non-leukemic myeloblasts in the post-chemotherapy setting. This overlap limits the diagnostic utility of TIM3 as a specific marker of neoplasia. © 2013 International Clinical Cytometry Society

Coagulation factor XIII subunit A (FXIIIa) intracellular expression has been described in platelets, megakaryocytes, monocytic cells, and leukemic blasts. Flow cytometric-based studies have suggested prognostic implications of FXIIIa expression, especially within the acute promyelocytic leukemia (APL) subgroup of acute myeloid leukemia (AML); however, its prognostic correlate by immunohistochemistry (IHC) is unknown. The aims of this study were to (1) define the clinicopathologic features of FXIIIa IHC-positive AML and (2) compare APL with other AML subtypes. Eighty-seven bone marrow biopsies or clot/particle preparations from our institution were evaluated with FXIIIa IHC. The study cohort consisted of bone marrow evaluations of 36 consecutive pretherapy APL, 42 selected pretherapy non-APL AML, and 9 negative staging cases. FXIIIa IHC expression was correlated with clinical and pathologic features and overall survival (OS). Leukemic blast FXIIIa cytoplasmic positivity was noted in 56% (20/36) APL and 74% (31/42) non-APL AML (P=0.10). FXIIIa IHC expression was associated with inferior OS within the APL cohort (P=0.04). No OS differences were noted in comparing FXIIIa IHC expression in all AML (P=0.17), or FXIIIa IHC expression within favorable, intermediate or adverse cytogenetic groups (P=0.14, 0.22 and 0.87, respectively). FXIIIa IHC expression is observed among a broad spectrum of AML subtypes and is not characterized by specific pathologic features. However, within the APL subgroup, FXIIIa IHC expression is associated with an inferior outcome and may be useful for additional prognostic risk stratification.

CD4+ small/medium pleomorphic T-cell lymphoma is a relatively rare subtype of cutaneous lymphoproliferative disorder with an indolent clinical behavior. The place of this condition among lymphomas is debatable. The authors describe a rare case of the direct association of CD4 small/medium pleomorphic T-cell lymphoma-like solitary nodule with Borrelia burgdorferi infection in a 5-year-old boy, discuss the reactive nature of this condition, and emphasize the importance of clinicopathological correlation.

Rollins-Raval M A & Roth C G (2012) Histopathology 60, 933–942 The value of immunohistochemistry for CD14, CD123, CD33, myeloperoxidase and CD68R in the diagnosis of acute and chronic myelomonocytic leukaemias Aims: In the absence of adequate aspirate films and touch imprints, distinction of chronic myelomonocytic leukaemia (CMML) from acute myeloid leukaemia with monocytic differentiation (Mo-AML) may be difficult solely on the basis of bone marrow biopsy morphological features. The aim of this study was to evaluate the diagnostic utility of a novel immunohistochemical panel for the diagnosis of acute and chronic myelomonocytic leukaemias in bone marrow biopsies. Methods and results: Immunohistochemical labelling for CD14, CD123, CD33, myeloperoxidase (MPO) and CD68R was assessed in 49 myeloid neoplasms with monocytic differentiation (24 CMMLs and 25 Mo-AMLs) and compared with that of 15 non-monocytic acute myeloid leukaemias (NM-AMLs) and 17 non-neoplastic controls. More than 20% CD14 immunohistochemistry (IHC)+ cells were seen only in Mo-AMLs and CMMLs, although Mo-AMLs showed wide variability and overlapped with other categories. More than 20% CD68R IHC+ cells had the highest sensitivity and specificity for Mo-AML. Discrepant MPO–/CD33+ expression was specific for Mo-AML but insensitive. A subset of blasts in Mo-AMLs and NM-AMLs were weakly CD123+. Conclusions: A significantly increased number of CD14+ cells raises the possibility of a myelomonocytic neoplasm but does not distinguish between CMML and Mo-AML. Significantly increased numbers of CD68R IHC+ cells and a discrepant MPO–/CD33+ staining pattern are specific for Mo-AML but are best utilized in a comprehensive panel.

Diagnostic hematopathology requires a multiparametric approach and integration of morphologic findings with the clinical, immunophenotypic, and other features. As hematopathology moves into an increasingly digital era, internet-deployed teaching sets consisting of whole slide images (WSI) and comprehensive ancillary information can help prepare hematopathology trainees for the future. Approximately 200 hematopathology conference cases over a 1-year period were de-identified, and case information (including clinical, microscopic and immunophenotypic features, flow cytometric histograms, and cytogenetic and molecular results) were entered into a database. Approximately 1,800 WSI were prepared by scanning using ×40 magnification, and WSI and supplemental data were stored on separate servers and referenced in the database via hyperlinks. From January 2009 to November 2011, the website has been accessed over 6,000 times. The user can view the list of cases and brief clinical history, with or without the diagnosis displayed. Once a case is chosen, the complete clinical history, WSI, case data, and other hyperlinks are displayed, and the user can also scroll down to see the diagnosis shown at the end of the case. Pre- and post-test evaluations are available for self-assessment. The hematopathology virtual set is emerging as an important tool in hematopathology education. The internet-deployed database is unique in the wide range of ancillary studies readily accessible, which reinforces the multiparametric approach in hematopathology.

Neoplastic erythroid proliferations may represent a diagnostic challenge owing to the difficulty in characterizing immature erythroblasts. Immunohistochemical expression of aldehyde dehydrogenase (ALDH), carbonic anhydrase isoenzyme I (CA I), and CD2-associated protein (CD2AP) was assessed in 66 bone marrow biopsy specimens and compared with glycophorin A and E-cadherin. ALDH, CA I, and CD2AP labeled neoplastic erythroblasts in most acute erythroid leukemias (AELs) and myelodysplasias and highlighted benign erythroid precursors within normal marrows, erythroid hyperplasias, acute lymphoblastic leukemias (ALLs), blastic plasmacytoid dendritic cell neoplasm, and most acute myeloid leukemias (AMLs). In 2 AELs, CD2AP was negative, and 1 AML lacked identifiable ALDH+ erythroid precursors. Immature erythroblasts were strongly ALDH+, weakly CA I+, weakly CD2AP±, E-cadherin±, and weakly glycophorin A±. AML was uncommonly weakly positive for ALDH, CA I, and CD2AP, and lymphoblasts from 1 ALL were weakly ALDH+. ALDH, CA I, and CD2AP are sensitive and relatively specific immunohistochemical markers for the erythroid lineage. ALDH is superior to glycophorin A and E-cadherin in highlighting immature erythroblasts.

Cytogenetic and molecular studies play a major role in myeloid disease subclassification and risk stratification. The 2008 World Health Organization (WHO) classification [1] recognizes several dise...

Lymphoplasmacytic infiltrates in the breast, a modified skin appendage, include lymphocytic lobulitis, other nonspecific benign proliferations, and mucosa-associated lymphoid tissue (MALT)-type lymphoma. Distinguishing these entities, all of which may be B-cell rich and may have associated sclerosis, can be difficult. In addition, the proportion that represents IgG4-related disease is unknown, and the similarity of MALT lymphomas to primary cutaneous marginal zone lymphoma is uncertain. To address these questions, the clinical, histologic, and immunohistochemical features of 50 benign and malignant breast lymphoplasmacytic infiltrates (10 lymphocytic lobulitis, 1 granulomatous, 19 not otherwise specified, 20 MALT lymphomas) were evaluated. Compared with the MALT lymphomas, benign cases had a less dense infiltrate (P < .001), fewer but more histologically apparent germinal centers (P < .001), and more marked fibrosis (P < .0001). Greater than 60% B cells were present in 23% (7/30) benign cases versus 75% (15/20) MALT lymphomas (P = .0003). Plasma cells were predominantly IgG+ in 83% (24/29) benign cases and predominantly IgM+ in 73% (14/19) MALT lymphomas (P < .0001). None of the benign cases had greater than 50 IgG4+ plasma cells/high-power field, and only 1 lymphocytic lobulitis case had an IgG4/IgG ratio exceeding 40% and no clinical evidence for extramammary IgG4-related disease. Although there may be some overlapping features, routine histopathology together with limited immunohistochemical stains can distinguish benign from neoplastic lymphoplasmacytic infiltrates in the breast. Despite frequent sclerosis, the breast is not a common site of unrecognized IgG4-related sclerosing disease. Although there are similarities, breast MALT lymphomas can be separated from cutaneous marginal zone lymphoma.

Virtual microscopy has been adopted by many medical schools but often without addressing the need for students to understand how to integrate slide observations with other diagnostic information. The goal of this study was to develop an innovative tool for teaching pathology to medical students that presents a variety of virtual materials necessary for a complete pathology evaluation. The Virtual Pathology Instructor (V-PIN) is patient simulation software (vpSim) created and supported by the University of Pittsburgh School of Medicine, Laboratory for Educational Technology, and allows students to assume the role of a diagnostic pathologist. V-PIN utility was demonstrated by educationally significant improvement between pretest and posttest scores for 2 cases (mean, 3.8 versus 4.2; P = .0007; 1.9 versus 3.0; P = .0001). A third case did not perform as well (mean, 2.5 versus 2.3; P = .12) but detailed evaluation of the performance of the case identified possible improvements. Maximum posttest performance was seen following both the traditional workshop and the V-PIN case as compared to the case alone (posttest 4.2 versus 3.0; P < .0001). No significant difference was identified in student progress through V-PIN cases taken before or after the related traditional workshop, as demonstrated by total time on task, number of steps to complete, total score, number of incorrect answers, and number of requests for V-PIN help. Patient simulation software is an effective tool for teaching pathology to medical students and can provide individual instruction and immediate feedback as well as identify opportunities to refine and enhance the educational experience.

Background: High grade B cell lymphoma (HGBL) is a heterogeneous entity with morphologic and genetic features intermediate between diffuse large B-cell lymphoma and Burkitt lymphoma (BL). Many patients with HGBL also have concurrent MYC, BCL2 and/or BCL6 rearrangements documented by FISH, the so-called double-hit lymphoma (DHL), which has now been defined as a separate entity in the updated WHO classification in 2016 as HGBL with rearrangements of MYC and BCL2 and/or BCL6. Other HGBL without MYC and BCL2 or BCL6 have been termed HGBL, NOS. HGBL, NOS and DHL are considered clinically aggressive. The best therapeutic approach for HGBL, NOS is unclear, and outcomes of patients with DHL in comparison to HGBL, NOS are not well established. Objective: The aim of this study was to evaluate and describe the outcomes and practice patterns for patients with HGBL, NOS. Additionally, we compared the survival of patients with HGBL, NOS to those with DHL. Materials and Methods: This retrospective cohort study was conducted at the University of Pittsburgh Medical Center. All patients identified as HGBL by pathology review at the University of Pittsburgh Hematopathology Department from 2010-2014 were included. Outcomes between standard therapy with R-CHOP and high intensity therapies with either R-EPOCH or R-HyperCVAD were compared for those patients with HGBL. Survival curves were generated with the Kaplan-Meier method, and overall survival was compared using the log-rank test. Cox-regression analysis was used to adjust for covariates. Results: 50 patients with newly diagnosed HGBL without a double-hit genotype were identified. Of these patients, 38 received R-CHOP (63%), R-EPOCH (21%) or R-HyperCVAD (16%). Baseline characteristics between treatment groups (Table 1) revealed an older age (p=0.033) and more frequent germinal center genotype (p=0.023) in those treated with R-CHOP. Median follow-up for this group was 18 months. There was no difference in the overall survival (OS) between R-CHOP and higher intensity regimens (p=0.540) (Figure 1). Median survival was not reached in either group. 2-year survival was 76%. Only a high-risk IPI score retained prognostic significance with OS in multivariate analysis (p=0.022). This compares favorable to 13 cases of DHL treated with R-CHOP, R-EPOCH, or R-HyperCVAD during a similar time period for whom the median overall survival was 8.9 months (p=0.016) Conclusion: Both standard therapy with R-CHOP and higher intensity therapies appear to be effective in the treatment of HGBL without double-hit genotype. IPI score remains prognostically significant. Outcomes in patients with HGBL, NOS appear favorable in comparison with patients with DHL. Figure Figure. Disclosures No relevant conflicts of interest to declare.

Establishing the diagnosis of myelodysplastic syndrome (MDS) can be difficult and requires a multiparametric approach, with correlation of the clinical, morphologic and genetic features. Although M...

FLT3-ITD and NPM1 mutation testing in acute myeloid leukemia (AML) plays an important role in prognostic risk stratification, especially within the intermediate cytogenetic risk group. Molecular studies require adequate fresh material and are typically performed on a dedicated aspirate specimen, which may not be available in all cases. Prior flow cytometric studies have suggested an association between CD123 overexpression in AML and FLT3-ITD and/or NPM1 mutations; however, the immunohistochemical (IHC) correlate is unknown. We assessed CD123 IHC expression in 157 AML bone marrow biopsies and/or marrow particle preparations, and correlated with the morphologic, immunophenotypic, and cytogenetic features and with the presence of FLT3-ITD and NPM1 mutations. We found that CD123 IHC expression, seen in 40% of AML, occurred across a wide spectrum of 2008 World Health Organization subtypes and was most frequent within the intermediate risk group. As compared with CD123 IHC-AML, CD123 IHC+AML demonstrated higher marrow blast percentages (median 69%), monocytic differentiation (33/63 cases), and CD34 negativity (29/63 cases). Eighty-three percent (25/30) FLT3-ITD-mutated AML were CD123+ (P

Plasmacytoid dendritic cells, which play a fundamental role in the innate immune response, are best known for their presence in hyaline-vascular Castleman disease and histiocytic necrotizing lymphadenitis. The relative number and distribution in many reactive entities as detected using more sensitive methods are uncertain, and their diagnostic implications are unknown. Immunohistochemical studies for plasmacytoid dendritic cell-associated markers CD123 and CD2AP were performed on 42 lymph nodes with hyaline-vascular Castleman disease, histiocytic necrotizing lymphadenitis, sarcoidosis, necrotizing granulomatous inflammation, viral infection, dermatopathic lymphadenopathy, autoimmune disease, and a histologic pattern compatible with toxoplasmosis. The overall plasmacytoid dendritic cell numbers and growth patterns (tight aggregates, loose aggregates/clusters, scattered single cells) were assessed. Plasmacytoid dendritic cells were present in all cases and were predominantly distributed in loose aggregates/clusters or singly. They were most numerous in granulomatous inflammation and histiocytic necrotizing lymphadenitis, whereas viral infections showed the fewest overall numbers and a predominant pattern of scattered single cells. Tight aggregates of plasmacytoid dendritic cells were most numerous in hyaline-vascular Castleman disease (100% sensitive, 68% specific). Plasmacytoid dendritic cells are not limited to a small number of reactive lymphadenopathies but are found in many reactive processes, often with a predominant pattern of loose aggregates/clusters and scattered single cells. However, tight aggregates were a characteristic feature of hyaline-vascular Castleman disease, and viral infections typically showed only few scattered cells distributed singly.

In the absence of adequate aspirate films and touch imprints, distinction of chronic myelomonocytic leukaemia (CMML) from acute myeloid leukaemia with monocytic differentiation (Mo-AML) may be difficult solely on the basis of bone marrow biopsy morphological features. The aim of this study was to evaluate the diagnostic utility of a novel immunohistochemical panel for the diagnosis of acute and chronic myelomonocytic leukaemias in bone marrow biopsies.Immunohistochemical labelling for CD14, CD123, CD33, myeloperoxidase (MPO) and CD68R was assessed in 49 myeloid neoplasms with monocytic differentiation (24 CMMLs and 25 Mo-AMLs) and compared with that of 15 non-monocytic acute myeloid leukaemias (NM-AMLs) and 17 non-neoplastic controls. More than 20% CD14 immunohistochemistry (IHC)+ cells were seen only in Mo-AMLs and CMMLs, although Mo-AMLs showed wide variability and overlapped with other categories. More than 20% CD68R IHC+ cells had the highest sensitivity and specificity for Mo-AML. Discrepant MPO-/CD33+ expression was specific for Mo-AML but insensitive. A subset of blasts in Mo-AMLs and NM-AMLs were weakly CD123+.A significantly increased number of CD14+ cells raises the possibility of a myelomonocytic neoplasm but does not distinguish between CMML and Mo-AML. Significantly increased numbers of CD68R IHC+ cells and a discrepant MPO-/CD33+ staining pattern are specific for Mo-AML but are best utilized in a comprehensive panel.

Pediatric-type nodal follicular lymphoma (PTNFL) is a variant of follicular lymphoma (FL) characterized by localized presentation and excellent behavior despite its often high-grade histologic appearance. We recently identified high proliferation index and the absence of BCL2, BCL6, and IRF4 gene rearrangements as defining features of PTNFL in both children and adults (Louissaint, Blood 2012). In contrast to typical FL, children with PTNFL consistently have persistent remissions after surgical excision alone. Therefore, it is critically important to identify PTNFL in order to avoid unnecessary therapy. Considering the unique clinical behavior of PTNFL, we hypothesized that the mutational landscape of this disease would differ from that of typical FL. Twenty-four cases were collected from several institutions (MGH, Brigham & Women's, Weill Cornell, Chicago Children's, Boston Children's, University of Pittsburgh, SUNY Downstate, and Stanford). PTNFL was defined by the following criteria: 1) nodal involvement, 2) architectural effacement by a clonal follicular proliferation, 3) high proliferation index and 4) absence of both MUM1/IRF4 expression and BCL2/BCL6 rearrangements by FISH. All cases presented with localized nodal involvement and demonstrated no evidence of recurrence or progression after chemotherapy (n=5), radiation (n=3) or surgical excision alone (n=13) (therapeutic approach to be confirmed in 3 cases), with a median follow-up of 33.1 months (range 10-124 months). Subjects ranged in age from 4-60 years, including 14 children (4-18 years; median 15) and 10 adults (20-60 years; median 29.5). Whole exome sequencing performed on 7 PTNFL cases showed a strikingly low mutation burden (7.1 non-silent mutations/exome), more than an order of magnitude lower than the exomic mutation burden of typical FLs (Green, PNAS 2015; Pasqualucci, Cell Rep 2015). Given these findings, we pursued targeted exome capture and next-generation sequencing for 112 genes previously reported to be recurrently mutated in FL across a panel of 20 PTNFLs. Targeted sequencing (mean depth, 250) again demonstrated very low mutation burden in PTNFL, with a median number of non-silent mutations of 1.67/case compared with 4 mutations/case (P Disclosures South: Lineagen Corporation: Consultancy; ARUP Laboratories: Employment; Affymetrix: Consultancy, Honoraria; Illumina: Consultancy, Honoraria. Hasserjian:Promedior: Consultancy.

IgG4-related sclerosing disease (IRSD) is a steroid-responsive fibroinflammatory disorder characterized by increased IgG4+ cells. Nodal involvement usually lacks the dense sclerosis seen in extranodal sites, with histologic patterns overlapping with other reactive processes. Twenty-six lymph nodes showing IRSD-related histologic patterns were evaluated for IgG and IgG4 positive cells by immunohistochemistry and correlated with the clinical features. Cases included 7 Castleman disease–like cases (type I pattern), 10 follicular hyperplasia (type II), and 9 plasmacytosis (type III). The mean numbers of IgG4+ cells per high-power field (HPF) were 4.8 (I), 8.4 (II), and 26.6(III), and the mean IgG4/IgG ratios were 0.05 (I), 0.04 (II), and 0.08 (III). Using >50 IgG4+cells/HPF and IgG4/IgG ratio of >0.4 for absolute and relative increases, only 1 case fulfilled both criteria for increased IgG4+ cells, a patient with Hashimoto’s thyroiditis without clinical evidence of IRSD. The results suggest that increased IgG4+ cells may rarely be seen in non-IRSD lymph nodes.