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* Context.--Digital pathology using whole slide images has been recently approved to support primary diagnosis in clinical surgical pathology practices. Here we describe a novel imaging method, fluorescence-imitating brightfield imaging, that can capture the surface of fresh tissue without requiring prior fixation, paraffin embedding, tissue sectioning, or staining. Objective.--To compare the ability of pathologists to evaluate direct-to-digital images with standard pathology preparations. Design.--One hundred surgical pathology samples were obtained. Samples were first digitally imaged, then processed for standard histologic examination on 4-im hematoxylin-eosin-stained sections and digitally scanned. The resulting digital images from both digital and standard scan sets were viewed by each of 4 reading pathologists. The data set consisted of 100 reference diagnoses and 800 study pathologist reads. Each study read was compared to the reference diagnosis, and also compared to that reader's diagnosis across both modalities. Results.--The overall agreement rate, across 800 reads, was 97.9%. This consisted of 400 digital reads at 97.0% versus reference and 400 standard reads versus reference at 98.8%. Minor discordances (defined as alternative diagnoses without clinical treatment or outcome implications) were 6.1% overall, 7.2% for digital, and 5.0% for standard. Conclusions.--Pathologists can provide accurate diagnoses from fluorescence-imitating brightfield imaging slide-free images. Concordance and discordance rates are similar to published rates for comparisons of whole slide imaging to standard light microscopy of glass slides for primary diagnosis. It may be possible, therefore, to develop a slide-free, nondestructive approach for primary pathology diagnosis., While in vivo methods for disease detection and classification, including radiology and liquid biopsy, continue to improve with respect to spatial resolution (radiology) and molecular information, they have not, to [...]

Context.--Malignant mesothelioma (MM) is an uncommon tumor that can be difficult to diagnose.Objective.--To provide updated, practical guidelines for the pathologic diagnosis of MM.Data Sources.--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.Conclusions.--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.(Arch Pathol Lab Med. 2018;142:89-108; doi: 10.5858/arpa.2017-0124-RA), The pathologic diagnosis of malignant mesothelioma (MM) continues to evolve and be refined as more antibodies and molecular tests become available for general use. This is especially applicable to distinguishing [...]

Context.--There are a number of critical factors that can lead to incorrect results if the diagnostic pathologist performing immunohistochemistry is unaware of, or not vigilant about, their influence. Objective.--To highlight 3 arenas in which errors may be introduced. Data Sources.--For choosing the correct primary antibody, selection of the most appropriate antibodies for a given clinical application can be aided by obtaining information from the vendor; however, this can yield incomplete information. There are a number of online databases that have comparisons of antibodies from different vendors, particularly with respect to their use and properties. Reading the published literature can assist in this process, particularly with respect to determining antibody sensitivity and specificity, but it is a daunting task to keep up with all of the immunohistochemistry-related papers published. Finally, Web sites of a number of quality assurance organizations are accessible and can provide a wealth of information comparing the 'real world' performance characteristics of different antibodies to the same target protein. False-positive signals can result from a number of factors, including the use of inappropriately high antibody concentration, and 'pseudospecific' signal that is in the wrong compartment of the cell. False-negative signal can result from factors such as use of a nonoptimized epitope retrieval method. It is critical that epitope retrieval methods be optimized for each antibody employed in the laboratory. Conclusions.--By paying attention to these potential problems, the 'black box' of diagnostic immunohistochemistry can be made more transparent. (Arch Pathol Lab Med. 2016; 140:893-898; doi: 10.5858/arpa.2016-0119-RA), The great British science fiction writer, inventor, and futurist Arthur C. Clarke noted that 'any sufficiently advanced technology is indistinguishable from magic.' (1) Immunohistochemistry (IHC), a technique invented in the [...]

The HER-2 oncoprotein is overexpressed in 20% to 30% of invasive breast tumors, and its presence confers important prognostic information. Accurate testing for HER-2 in breast cancer can be achieved using immunohistochemistry with complementary fluorescence in situ hybridization (FISH) testing, taking advantage of the strength of each of these technologies.

Context.--Identification of the site of origin of carcinoma of unknown primary using immunohistochemistry is a frequent requirement of anatomic pathologists. Diagnostic accuracy is crucial, particularly in the current era of targeted therapies and smaller sample sizes. Objectives.--To provide practical guidance and suggestions for classifying carcinoma of unknown primary using both proven and new antibodies, as well as targeting panels based on integration of morphologic and clinical features. Data Sources.--Literature review, the authors' practice experience, and authors' research. Conclusions.--With well-performed and interpreted immunohistochemistry panels, anatomic pathologists can successfully identify the site of origin of carcinoma of unknown primary. It is crucial to understand not only the diagnostic uses of the many available antibodies but also the potential limits and pitfalls. (Arch Pathol Lab Med. 2016; 140:508-523; doi: 10.5858/arpa.2015-0173-CP), It is estimated that approximately 4% of all patients with cancer present with carcinomas of unknown primary (CUPs), representing a higher incidence than known malignancies such as non-Hodgkin lymphoma or [...]

Aims: Neuroendocrine neoplasms (NNs) range from well to poorly differentiated and indolent to highly aggressive. The site of origin in metastatic NNs has therapeutic and prognostic implications. SATB2 is a transcriptional regulator involved in osteoblastic and neuronal differentiation and is a sensitive and specific marker of colorectal epithelium. This study aimed to evaluate the expression of SATB2 in NNs from various primary sites and its utility as a marker in determining the site of origin of these neoplasms. Methods and results: SATB2 immunohistochemistry was performed on 266 NNs, including lung small cell carcinomas (n = 39) and carcinoids (n = 30), bladder (n = 21) and prostate (n = 31) small cell carcinomas, and gastrointestinal (GI)/pancreatic NNs of various primary sites (n = 145) consisting of well‐differentiated neuroendocrine tumours (WDNET)s (n = 124) and poorly differentiated neuroendocrine carcinomas (PDNEC)s (n = 21). SATB2 was expressed in prostatic (10 of 31, 32%) and bladder (eight of 21, 38%) small cell carcinomas, lung carcinoid tumours (one of 30, 3%), and lung small cell carcinomas (eight of 39, 21%). Among primary GI NNs, SATB2 was expressed in 37 of 124 (30%) WDNETs and four of 21 (19%) PDNECs. Of the former, 15 of 15 (100%) rectal/rectosigmoid and 22 of 22 (100%) appendiceal neoplasms expressed SATB2. Using receiver operator characteristic analysis, SATB2 was a sensitive and specific marker for rectal (100.0%, 80.0%) and appendiceal (100.0%, 84.5%) WDNETs, respectively. Conclusions: In summary, SATB2 is a sensitive and specific marker for rectal/rectosigmoid and appendiceal WDNETs, and may represent a useful diagnostic tool when these sites of origin are considered in the differential diagnosis. [ABSTRACT FROM AUTHOR]

Context.--Numerous immunohistochemical stains have been shown to exhibit exclusive or preferential positivity in breast myoepithelial cells relative to their luminal/epithelial counterparts. These myoepithelial markers provide invaluable assistance in accurately classifying breast proliferations, especially in core biopsies. Although numerous myoepithelial markers are available, they differ in their sensitivity, specificity, and ease of interpretation, which may be attributed, to a large extent, to the variable immunoreactivity of these markers in stromal cells including myofibroblasts, vessels, luminal/epithelial cells, and tumor cells. Objective.--To review commonly used myoepithelial markers in breast pathology and a selection of diagnostic scenarios where they may be useful. Data Sources.--The information outlined in this review article is based on our experiences with routine cases and a review of English-language articles published between 1987 and 2008. Conclusions.--To demonstrate the presence or absence of myoepithelial cells, a panel-based approach of 2 or more markers is recommended. Markers that most effectively combine sensitivity, specificity, and ease of interpretation include smooth muscle myosin heavy chains, calponin, p75, p63, P-cadherin, basal cytokeratins, maspin, and CD10. These markers, however, display varying cross-reactivity patterns and variably reduced expression in the myoepithelial cells bordering in situ carcinomas. The choice of a myoepithelial marker should be dependent on a combination of factors, including published evidence on its diagnostic utility, its availability, performance characteristics that have been achieved in a given laboratory, and the specific diagnostic scenario. When its use is deemed necessary, immunohistochemistry for myoepithelial cells in breast pathology is most effective when conceptualized as supplemental, rather than central to routine morphologic interpretation., At the light microscopic level, 2 distinct cell populations can be recognized lining the human mammary ductal and terminal ductolobular units: a luminally located layer of polarized epithelial cells and [...]