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* Context.--Next-generation sequencing--based approaches using RNA have increasingly been used by clinical laboratories for the detection of fusion genes, intragenic rearrangements, and exon-skipping events. Correspondingly, the College of American Pathologists (CAP) has advanced RNA sequencing proficiency testing (PT) to ensure optimal performance of these assays. Objective.--To report on laboratory performance and practices of RNA sequencing for the detection of fusion genes, intragenic rearrangements, and exon-skipping events using CAP PT data from 8 mailings (2018-A through 2021-B). Design.--CAP PT RNA sequencing program results from 153 laboratories across 24 proficiency test specimens, interrogating 22 distinct engineered fusion transcripts, were analyzed for correct identification of the fusion event, associated performance variables, and laboratory practices. Results.--Overall, the 4-year program detection rate (sensitivity) was 95.5% (1486 of 1556 results). False-negative rates were 3.6% (53 of 1463) and 18.3% (17 of 93) for fusion gene and intragenic rearrangement/exon-skipping events, respectively. Only 19 false-positive results were reported among the 8 PT mailings, and most were likely the result of preanalytical or postanalytical errors. There were no practice characteristics (eg, instrumentation, sequencing method) significantly associated with the fusion detection results. Conclusions.--These data reveal a high overall sensitivity and specificity for fusion gene detection by participating laboratories using clinical RNA sequencing. Performance was comparable across all laboratories, regardless of methodology. The fraction of false-negative results for intragenic rearrangement/exon-skipping events was greater than that for the chimeric fusion genes. False-negative results could not be attributed to any specific practice characteristics. [ABSTRACT FROM AUTHOR]

This article discusses a rare and diagnostically challenging soft-tissue tumor called myxoid "pauci-hemosiderotic" fibrolipomatous tumor (HFLT). HFLT is characterized by an admixture of CD34-positive spindle cells, mature adipocytes, and hemosiderin-laden macrophages. It typically occurs in the subcutis of the distal lower extremities and has a local recurrence rate of up to 50%. Cytogenetic studies have identified translocations involving the TGFBR3 and OGA genes in most HFLT cases. The article presents a case study of a 38-year-old transgender male with a myxoid pHFLT tumor and highlights the challenges in diagnosing this rare entity. [Extracted from the article]

Context.--Therapy targeted at human epidermal growth factor receptor 2 (HER2; also known as ERBB2) was used initially for breast and gastroesophageal carcinoma and has more recently been adopted for endometrial serous carcinoma (ESC) and colorectal carcinoma (CRC). There is evidence that predictive biomarker testing algorithms for HER2 must be tumor type specific and that an algorithm validated for one tumor type cannot be applied to another. Objective.--To describe current laboratory practices for HER2 assessment in ESC and CRC. Design.--We surveyed laboratories participating in the 2021 College of American Pathologists (CAP) HER2 immunohistochemistry proficiency testing program. Results.--The survey was distributed to 1548 laboratories and returned by 1195, of which 83.5% (998) were in the United States. For ESC, 24.0% (287) of laboratories reported performing in-house testing for HER2 by immunohistochemical staining and/or in situ hybridization; of these, 44.3% (127) performed it reflexively on all cases of ESC. The most common criterion for evaluating HER2 was the American Society of Clinical Oncology/CAP 2018 guideline for breast carcinoma (69.0%; 194 of 281), whereas only 16.0% (45) of laboratories used guidelines specific to ESC. For CRC, 20.2% (239 of 1185) of laboratories performed in-house HER2 testing, and 82.0% of these (196) did the test only at the clinician's request. A plurality (49.4%; 115 of 233) used gastroesophageal cancer guidelines when scoring CRC, 30.0% (70) used the CRC scoring system from the HERACLES trial, and 16.3% (38) used the American Society of Clinical Oncology/CAP 2018 guideline for breast carcinoma. Conclusions.--Laboratories vary in their approach to HER2 testing in ESC and CRC. Most laboratories did not report using tumor type--specific recommendations for HER2 interpretation. The lack of standardization could present a challenge to evidence-based practice when considering targeted therapy for these diseases. [ABSTRACT FROM AUTHOR]

Myofibroblastoma is a rare, benign stromal tumor with a diverse morphologic spectrum. Mammary-type myofibroblastoma (MTMF) is the extra-mammary counterpart of this neoplasm and its occurrence throughout the body has become increasingly recognized. Similar morphologic variations of MTMF have now been described which mirror those seen in the breast. We describe a case of intra-abdominal MTMF composed of short fascicles of eosinophilic spindle cells admixed with mature adipose tissue. The spindle cells stained diffusely positive for CD34, desmin, smooth muscle actin, and h-caldesmon by immunohistochemistry. Concurrent loss of RB1 (13q14) and 13q34 loci were confirmed by fluorescence in situ hybridization whereas anchored multiplex PCR and whole transcriptome sequencing did not reveal any pathognomonic fusions suggesting an alternative diagnosis. To the best of our knowledge this is the first documented case of leiomyomatous variant of MTMF. [ABSTRACT FROM AUTHOR]

Dermatofibrosarcoma protuberans (DFSP) is a mesenchymal neoplasm that is usually located in the dermis or subcutis and is locally aggressive. Rarely, these lesions may undergo fibrosarcomatous transformation, which is thought to increase their metastatic potential. DFSP is classically associated with a 17;22 translocation (or ring chromosome thereof) resulting in fusion of the COL1A1 and PDGFB genes. However, variant fusions involving PDGFD have been recently reported. Herein, we present two morphologically diverse cases of DFSP with PDGFD rearrangement. Case 1 is a 68-year-old female with a left dorsal foot lesion. Morphologically, the lesion is unusual as it is a well-circumscribed, hypercellular, subcutaneous nodule with uniform CD34-positive spindle cells arranged in a herringbone pattern without storiform arrangement or "honeycombing" fat entrapment. It was diagnosed as pure fibrosarcomatous DFSP. Case 2 is a 37-year-old male with a right supra-auricular lesion. Morphologically, the lesion displays classic DFSP features including bland CD34-positive spindle cells with storiform growth, fat entrapment, and infiltrative borders. Both lesions were negative for COL1A1-PDGFB fusion but positive for PDGFD rearrangement by fluorescence in situ hybridization (FISH) analysis. FISH testing for PDGFD rearrangement should be performed in cases where there is a high suspicion for DFSP but initial studies for COL1A1-PDGFB are negative. [ABSTRACT FROM AUTHOR]

"Cutaneous melanocytic tumor with CRTC1‐TRIM11 fusion" (CMTCT) is a newly described, potentially novel entity that typically presents as a dermal nodule on the head and neck, extremities, and trunk of adults. Histopathologically, it is reported as a nodular or multinodular tumor composed of epithelioid and spindle cells that are variably immunoreactive for S100‐protein, SOX10, and MITF along with more specific melanocytic markers such as MelanA and HMB45. With only 11 cases reported in the English literature so far, the neoplasm appears to behave in a relatively indolent fashion. Nevertheless, in one case, local recurrence and synchronous distant metastasis were evident after 13 years. Additional cases with longer follow‐up are essential to determine the neoplasm's biologic behavior with more accuracy. Herein, two cases of CMTCT, one arising on the lower back of a 65‐year‐old female and the other on the arm of a 33‐year‐old female in addition to a comprehensive literature review are reported. [ABSTRACT FROM AUTHOR]

Acral fibromyxoma (AF) is a slow growing benign soft tissue tumor with predilection to subungal and periungal region of the hands or feet. CD34 is consistently expressed whereas very recently loss of Rb1 expression was described as a possible driver molecular event for this entity. Herein we present two additional cases of AF with loss of Rb1 expression by IHC and subsequent confirmation of loss of the RB1 gene locus by fluorescence in situ hybridization (FISH). We hope to raise awareness in dermatopathology community of this new discovery, which can be diagnostically exploitable for this distinct and probably underreported neoplasm. [ABSTRACT FROM AUTHOR]

Context.--As laboratories increasingly turn from single-analyte testing in hematologic malignancies to nextgeneration sequencing--based panel testing, there is a corresponding need for proficiency testing to ensure adequate performance of these next-generation sequencing assays for optimal patient care. Objective.--To report the performance of laboratories on proficiency testing from the first 4 College of American Pathologists Next-Generation Sequencing Hematologic Malignancy surveys. Design.--College of American Pathologists proficiency testing results for 36 different engineered variants and/or allele fractions as well as a sample with no pathogenic variants were analyzed for accuracy and associated assay performance characteristics. Results.--The overall sensitivity observed for all variants was 93.5% (2190 of 2341) with 99.8% specificity (22 800 of 22 840). The false-negative rate was 6.5% (151 of 2341), and the largest single cause of these errors was difficulty in identifying variants in the sequence of CEBPA that is rich in cytosines and guanines. False-positive results (0.18%; 40 of 22 840) were most likely the result of preanalytic or postanalytic errors. Interestingly, the variant allele fractions were almost uniformly lower than the engineered fraction (as measured by digital polymerase chain reaction). Extensive troubleshooting identified a multifactorial cause for the low variant allele fractions, a result of an interaction between the linearized nature of the plasmid and the Illumina TruSeq chemistry. Conclusions.--Laboratories demonstrated an overall accuracy of 99.2% (24 990 of 25 181) with 99.8% specificity and 93.5% sensitivity when examining 36 clinically relevant somatic single-nucleotide variants with a variant allele fraction of 10% or greater. The data also highlight an issue with artificial linearized plasmids as survey material for next-generation sequencing. [ABSTRACT FROM AUTHOR]

Adenomyoepithelioma is an extremely rare primary cutaneous neoplasm. Although there is ample evidence on the existence of malignant adenomyoepithelioma in the breast, a malignant counterpart in the skin has not been documented. We report a primary cutaneous adenomyoepithelioma (pcAME) with malignant features arising from a spiradenoma in a 39-year-old female patient. The tumor was solid-cystic in appearance and entirely located in the subcutaneous tissue. Histologically, the tumor displayed foci of adenomatous changes and adenomyoepitheliomatous hyperplasia adjacent to a minute spiradenoma. Gradual increase of architectural complexity, cytologic atypia, mitotic activity, and infiltrative growth were observed in a significant portion of the neoplasm, indicative of transformation to adenomyoepithelioma and subsequently low- to high-grade salivary-type epithelial-myoepithelial carcinoma (EMCA). The intimate dual populations of ductal and myoepithelial cells were highlighted by a panel of immunohistochemical stains in all different components of the tumor. Molecular studies revealed a PIKCA3 mutation, a genetic aberration that has been documented in EMCA, particularly of breast origin. The current case documents for the first time a pcAME with malignant features arising from a spiradenoma and suggests adenomyoepithelioma ex spiradenoma as a possible tumorigenesis pathway of this rare cutaneous tumor. [ABSTRACT FROM AUTHOR]

Dermatofibrosarcoma protuberans (DFSP) is a translocation-associated, low-grade sarcoma with fibroblastic differentiation. It is the most common superficial sarcoma, almost exclusively arising within the dermis. In a minority of cases, there is a transition from the conventional morphology to a fibrosarcomatous pattern, known as a fibrosarcomatous DFSP (FS-DFSP). Although a number of different molecular alterations have been described to account for this transformation, it remains poorly understood. Herein we report the first case of a FS-DFSP with a fusion between ERG, an ETS family transcription factor, and MAP3K7CL, a kinase gene rarely observed in fusion gene events. [ABSTRACT FROM AUTHOR]

Context.--Fluorescence in situ hybridization (FISH) and brightfield in situ hybridization (ISH) are 2 clinically approved laboratory methods for detecting ERBB2 (HER2) amplification in breast cancer. Objective.--To compare the performance of FISH and brightfield ISH on proficiency testing administered by the College of American Pathologists Laboratory Accreditation Program. Design.--Retrospective review was performed on 70 tissue core samples in 7 separate proficiency testing surveys conducted between 2009 and 2013. Results.--The samples included 13 consensus-amplified tissue cores, 53 consensus-nonamplified cores, and 4 cores that did not reach consensus for FISH and/or brightfield ISH. There were 2552 individual responses for FISH and 1871 individual responses for brightfield ISH. Consensus response rates were comparable for FISH (2474 of 2524; 98.0%) and brightfield ISH (2135 of 2189; 97.5%). The FISH analysis yielded an average HER2 copy number per cell that was significantly higher (by 2.86; P = .02) compared with brightfield ISH for amplified cores. For nonamplified cores, FISH yielded slightly, but not significantly, higher (by 0.17; P = .10) HER2 copy numbers per cell. There was no significant difference in the average HER2 to control ratio for either consensus-amplified or consensus-nonamplified cores. Participants reported "unable to analyze" more frequently for brightfield ISH (244 of 2453; 9.9%) than they did for FISH (160 of 2684; 6.0%). Conclusions.--Our study indicates a high concordance rate in proficiency testing surveys, with some significant differences noted in the technical performance of these assays. In borderline cases, updated American Society of Clinical Oncology/College of American Pathologists cutoff thresholds that place greater emphasis on HER2 copy number per cell could accentuate those differences between FISH and brightfield ISH. [ABSTRACT FROM AUTHOR]

Dedifferentiated liposarcoma can arise de novo or as a complication of a preexisting well-differentiated liposarcoma. We describe the radiologic and pathologic features of a long-standing liposarcoma with multiple recurrences in a 59-year-old male. Imaging demonstrated a heterogeneous fat-containing mass in the anterior thigh. The adjacent proximal femur showed irregular cortical new bone, eventually followed by intramedullary osteoblastic involvement and pathologic fracture. Histologic assessment at resection revealed dedifferentiated liposarcoma with low-grade osteosarcomatous component. The patient subsequently developed metastatic lesions in the lungs containing osteoid and osteoblastic bone metastases. We discuss the radiologic and pathologic features of this rare entity that, to our knowledge, has previously been reported to directly involve osseous structures in only one other case and discuss the potential pitfalls in diagnosis. [ABSTRACT FROM AUTHOR]

The introduction of molecular testing into cytopathology laboratory practice has expanded the types of samples considered feasible for identifying genetic alterations that play an essential role in cancer diagnosis and treatment. Reverse transcription-polymerase chain reaction (RT-PCR), a sensitive and specific technical approach for amplifying a defined segment of RNA after it has been reverse-transcribed into its DNA complement, is commonly used in clinical practice for the identification of recurrent or tumor-specific fusion gene events. Real-time RT-PCR (quantitative RT-PCR), a technical variation, also permits the quantitation of products generated during each cycle of the polymerase chain reaction process. This review addresses qualitative and quantitative pre-analytic and analytic considerations of RT-PCR as they relate to various cytologic specimens. An understanding of these aspects of genetic testing is central to attaining optimal results in the face of the challenges that cytology specimens may present. Cancer Cytopathol 2017;125:11-19. © 2016 American Cancer Society. [ABSTRACT FROM AUTHOR]

Aims Breast sarcomas are rare, usually occurring in the setting of malignant phyllodes tumour ( MPT). Heterologous differentiation commonly resembles well-differentiated or pleomorphic liposarcoma. In extramammary sites, these subtypes have different biological behaviours and distinct genetic alterations: MDM2 and CDK4 amplification in well-differentiated liposarcoma, and polyploidy with complex structural rearrangements in pleomorphic liposarcoma. The aim of this study was to investigate foci resembling well-differentiated liposarcoma in MPT for MDM2 and CDK4 amplification. Methods and results We evaluated the clinicopathological characteristics of MPTs received by the Vanderbilt Breast Consultation Service containing components resembling well-differentiated or pleomorphic liposarcoma. Cases with available tissue blocks were subjected to fluorescence in-situ hybridization with MDM2 and CDK4 probes. Thirty-eight MPTs with liposarcomatous components were available for review. The mean patient age was 49.8 years (range 26-84 years). In addition to well-differentiated liposarcoma, the following components were also present: high-grade undifferentiated sarcoma ( n = 9; 23.7%), pleomorphic liposarcoma ( n = 4; 10.5%), non-high-grade sarcoma not otherwise specified ( n = 22; 57.9%), and malignant peripheral nerve sheath tumour-like ( n = 2; 5.2%). Among 10 cases tested, none showed amplification of MDM2 or CDK4. Conclusions This study examined molecular changes in the well-differentiated liposarcomatous components of MPT. Despite histological similarity to well-differentiated liposarcoma of soft tissues, liposarcomatous differentiation in MPT lacks the molecular phenotype characteristic of extramammary well-differentiated liposarcoma. [ABSTRACT FROM AUTHOR]

Context.-The College of American Pathologists surveys are the largest laboratory peer comparison programs in the world. These programs allow laboratories to regularly evaluate their performance and improve the accuracy of the patient test results they provide. Proficiency testing is offered twice a year to laboratories performing microsatellite instability testing. These surveys are designed to emulate clinical practice, and some surveys have more challenging cases to encourage the refinement of laboratory practices. Objective.-This report summarizes the results and trends in microsatellite instability proficiency testing from participating laboratories from the inception of the program in 2005 through 2012. Design.-We compiled and analyzed data for 16 surveys of microsatellite instability proficiency testing during 2005 to 2012. Results.-The number of laboratories participating in the microsatellite instability survey has more than doubled from 42 to 104 during the 8 years analyzed. An average of 95.4% of the laboratories correctly classified each of the survey test samples from the 2005A through 2012B proficiency challenges. In the 2011B survey, a lower percentage of laboratories (78.4%) correctly classified the specimen, possibly because of overlooking subtle changes of microsatellite instability and/or failing to enrich the tumor content of the specimen to meet the limit of detection of their assay. Conclusions.-In general, laboratories performed well in microsatellite instability testing. This testing will continue to be important in screening patients with colorectal and other cancers for Lynch syndrome and guiding the management of patients with sporadic colorectal cancer. [ABSTRACT FROM AUTHOR]

Mixed neuronal-glial tumors are rare and challenging to subclassify. One recently recognized variant, papillary glioneuronal tumor ( PGNT), is characterized by prominent pseudopapillary structures and glioneuronal elements. We identified a novel translocation, t(9;17)(q31;q24), as the sole karyotypic anomaly in two PGNTs. A fluorescence in situ hybridization ( FISH)-based positional cloning strategy revealed SLC44A1, a member of the choline transporter-like protein family, and PRKCA, a protein kinase C family member of serine/threonine-specific protein kinases, as the 9q31 and 17q24 breakpoint candidate genes, respectively. Reverse transcription-polymerase chain reaction ( RT-PCR) analysis using a forward primer from SLC44A1 exon 5 and a reverse primer from PRKCA exon 10 confirmed the presence of a SLC44A1-PRKCA fusion product in both tumors. Sequencing of each chimeric transcript uncovered an identical fusion cDNA junction occurring between SLC44A1 exon 15 and PRKCA exon 9. A dual-color breakpoint-spanning probe set custom-designed for interphase cell recognition of the translocation event identified the fusion in a third PGNT. These results suggest that the t(9;17)(q31;q24) with the resultant novel fusion oncogene SLC44A1-PRKCA is the defining molecular feature of PGNT that may be responsible for its pathogenesis. The FISH and RT-PCR assays developed in this study can serve as valuable diagnostic adjuncts for this rare disease entity. [ABSTRACT FROM AUTHOR]

Context.-Soft tissue pathology encompasses a remarkably diverse assortment of benign and malignant soft tissue tumors. Rendering a definitive diagnosis is complicated not only by the large volume of existing histologic subtypes (>100) but also frequently by the presence of overlapping clinical, histologic, immunohistochemical, and/or radiographic features. During the past 3 decades, mesenchymal tumor-specific, cytogenetic and molecular genetic abnormalities have demonstrated an increasingly important, ancillary role in mesenchymal tumor diagnostics. Objectives.-To review molecular diagnostic tools available to the pathologist to further classify specific soft tissue tumor types and recurrent aberrations frequently examined. Advantages and limitations of individual approaches will also be highlighted. Data Sources.-Previously published review articles, peer-reviewed research publications, and the extensive cytogenetic and molecular diagnostic experience of the authors to include case files of The University of Nebraska Medical Center. Conclusions.-Cytogenetic and molecular genetic assays are used routinely for diagnostic purposes in soft tissue pathology and represent a powerful adjunct to complement conventional microscopy and clinicoradiographic evaluation in the formulation of an accurate diagnosis. Care should be taken, however, to recognize the limitations of these approaches. Ideally, more than one technical approach should be available to a diagnostic laboratory to compensate for the shortcomings of each approach in the assessment of individual specimens. [ABSTRACT FROM AUTHOR]

Sarcomas constitute a heterogeneous group of rare tumors that in recent years have been shown by cytogenetic analysis to have a remarkably high incidence of specific and primary alterations. These genetic alterations not only have guided molecular studies in establishing the underlying genes involved, thereby yielding important pathogenetic information, but have also provided clinicians with a valuable tool to add to their diagnostic armamentarium. The addition of molecular cytogenetic (fluorescence in situ hybridization [FISH]) and molecular approaches (reverse transcriptase-polymerase chain reaction [RT-PCR]) has further enhanced the sensitivity and accuracy of detecting nonrandom chromosomal imbalances and/or structural rearrangements in sarcomas, including assessment in formalin-fixed, paraffin-embedded tissues. Poorly differentiated sarcomas represent a significant challenge to the pathologist as these neoplasms lack an identifiable hematoxylin and eosin-stained phenotype and often have lost diagnostic immunohistochemical or ultrastructural features as well. In contrast, primary cytogenetic changes and associated molecular events such as the 11;22 translocation in Ewing sarcoma are retained as a given tumor metastasizes or becomes less differentiated, as their presence appears to be vital for sustaining neoplastic transformation. Consequently, demonstration of characteristic, tumor-specific chromosomal aberrations is especially useful in the management of poorly differentiated sarcomas. [ABSTRACT FROM AUTHOR]

A reciprocal t(11;22)(q24;q12) is found in 85% of Ewing sarcomas (ES) cases. We report a case of a child with ES, in whom trisomy 8 was observed as the sole chromosomal abnormality. Fluorescence in situ hybridization—using a set of probes that localize to 22q12 (EWS) and 11q24 (FLI-1) and usually show the translocation as fusion (red-green) signal on der(22)—showed a fusion signal on der(11) suggesting an insertion as the mechanism that led to the EWS-FLI-1 gene rearrangement. Reverse transcriptase-polymerase chain reaction studies revealed the presence of two EWS/FLI1 fusion gene products. [Copyright &y& Elsevier]

A letter to the editor is presented regarding a case study of a 79-year-old female who underwent immunohistochemistry, which showed negative high-molecular-weight transmembrane glycoprotein (MUC 4), and confirmed to have positive FUS rearranged low-grade fibromyxoid sarcoma (LGFMS).

* Context.--The diagnosis and clinical management of patients with diffuse gliomas (DGs) have evolved rapidly over the past decade with the emergence of molecular biomarkers that are used to classify, stratify risk, and predict treatment response for optimal clinical care. Objective.--To develop evidence-based recommendations for informing molecular biomarker testing for pediatric and adult patients with DGs and provide guidance for appropriate laboratory test and biomarker selection for optimal diagnosis, risk stratification, and prediction. Design.--The College of American Pathologists convened an expert panel to perform a systematic review of the literature and develop recommendations. A systematic review of literature was conducted to address the overarching question, "What ancillary tests are needed to classify DGs and sufficiently inform the clinical management of patients?" Recommendations were derived from quality of evidence, open comment feedback, and expert panel consensus. Results.--Thirteen recommendations and 3 good practice statements were established to guide pathologists and treating physicians on the most appropriate methods and molecular biomarkers to include in laboratory testing to inform clinical management of patients with DGs. Conclusions.--Evidence-based incorporation of laboratory results from molecular biomarker testing into integrated diagnoses of DGs provides reproducible and clinically meaningful information for patient management. [ABSTRACT FROM AUTHOR]

Abstract: Cytogenetic analysis of a case of metastatic granulosa cell tumor recurring 21 years after oophorectomy revealed monosomy 22. This anomaly, typical of granulosa cell tumor, coupled with the pathologic and immunophenotypic findings assisted in establishing the proper diagnosis of this lesion in the absence of the original histopathologic slides. [Copyright &y& Elsevier]

Porocarcinoma is a rare malignant adnexal tumor with predilection for the lower extremities and the head and neck region of older adults. This entity may arise de novo or in association with a benign poroma. Porocarcinoma's non‐specific clinical appearance, immunohistochemical profile, and divergent differentiation may occasionally be diagnostically challenging. Recently, highly recurrent YAP1 and NUTM1 gene rearrangements have been described in cases of poroma and porocarcinoma. In this report, we present a case of porocarcinoma with squamous differentiation in an 81‐year‐old woman which harbored rearrangement of the YAP1 and NUTM1 loci and was diffusely immunoreactive for NUTM1. We discuss the recent advancements in the pathogenesis of poromas and porocarcinomas with emphasis on the clinical utility of the NUTM1 antibody. [ABSTRACT FROM AUTHOR]

Intracranial mesenchymal tumor (IMT), FET::CREB fusion-positive is a provisional tumor type in the 2021 WHO classification of central nervous system tumors with limited information available. Herein, we describe five new IMT cases from four females and one male with three harboring an EWSR1::CREM fusion and two featuring an EWSR1::ATF1 fusion. Uniform manifold approximation and projection of DNA methylation array data placed two cases to the methylation class "IMT, subclass B", one to "meningioma-benign" and one to "meningioma-intermediate". A literature review identified 74 cases of IMTs (current five cases included) with a median age of 23 years (range 4–79 years) and a slight female predominance (female/male ratio = 1.55). Among the confirmed fusions, 25 (33.8%) featured an EWSR1::ATF1 fusion, 24 (32.4%) EWSR1::CREB1, 23 (31.1%) EWSR1::CREM, one (1.4%) FUS::CREM, and one (1.4%) EWSR1::CREB3L3. Among 66 patients with follow-up information available (median: 17 months; range: 1–158 months), 26 (39.4%) experienced progression/recurrences (median 10.5 months; range 0–120 months). Ultimately, three patients died of disease, all of whom underwent a subtotal resection for an EWSR1::ATF1 fusion-positive tumor. Outcome analysis revealed subtotal resection as an independent factor associated with a significantly shorter progression free survival (PFS; median: 12 months) compared with gross total resection (median: 60 months; p < 0.001). A younger age (< 14 years) was associated with a shorter PFS (median: 9 months) compared with an older age (median: 49 months; p < 0.05). Infratentorial location was associated with a shorter overall survival compared with supratentorial (p < 0.05). In addition, the EWSR1::ATF1 fusion appeared to be associated with a shorter overall survival compared with the other fusions (p < 0.05). In conclusion, IMT is a locally aggressive tumor with a high recurrence rate. Potential risk factors include subtotal resection, younger age, infratentorial location, and possibly EWSR1::ATF1 fusion. Larger case series are needed to better define prognostic determinants in these tumors. [ABSTRACT FROM AUTHOR]

Primary superficial Ewing sarcoma (psES) cases are exceedingly rare, with fewer than 150 cases reported in the literature. Small case series have suggested differences between psES and Ewing sarcoma (ES) of bone or deep soft tissues: psES appears to have a more indolent course and a higher 5‐year overall survival rate. PsES is more common in older adolescent females as opposed to younger males in their peak growth velocity years in bone or deep soft tissue ES. We present a case report of a 17‐year‐old female with a relatively static nodule on her left thigh for 4 years. Morphologic, immunohistochemical, and molecular evaluations confirmed ES. Patient underwent a gross‐total resection and a shortened course of adjuvant chemotherapy without radiation. Cancer gene panel testing found three gene abnormalities (in addition to EWSR1‐FLI1 fusion): CCND1 copy number gain, ELF3 copy number loss, and TNFRSF14 copy number loss. To our knowledge, this is the first published case report of psES to include genomic sequencing and the first to report ELF3 and TNFRSF14 abnormalities in ES. Larger series of psES cases with genomic profiling are needed to elucidate a possible genetic etiology for its more indolent clinical course and favorable outcomes. [ABSTRACT FROM AUTHOR]

Context.--Detection of high-risk human papillomavirus (HR-HPV) in squamous cell carcinoma is important for classification and prognostication. In situ hybridization (ISH) is a commonly used HR-HPV--specific test that targets viral RNA or DNA. The College of American Pathologists (CAP) provides proficiency testing for laboratories performing HR-HPV ISH. Objective.--To compare the analytical performance of RNA- and DNA-based ISH methods on CAP HR-HPV proficiency tests. Design.--Data from the 2016-2018 CAP HPV ISH proficiency testing surveys were reviewed. These surveys consist of well-characterized samples with known status for HR-HPV, including 1 to 2 copies, 50 to 100 copies, 300 to 500 copies, and no copies of HR-HPV per cell. Results.--Ninety-five participants submitted 1268 survey results from 20 cores. Overall, RNA ISH had a significantly higher percentage of correct responses than DNA ISH: 97.4% (450 of 462) versus 80.6% (650 of 806) (P < .001). This disparity appears to be the consequence of a superior sensitivity of RNA ISH compared to DNA ISH for samples with 1 to 2 and with 50 to 100 copies of HRHPV per cell: 95.2% (120 of 126) versus 53.8% (129 of 240), P < .001, respectively, and 100% (89 of 89) versus 76.3% (119 of 156), P < .001, respectively. Conclusions.-An assessment of CAP HR-HPV proficiency test performance indicates that RNA ISH shows significantly higher accuracy than DNA ISH owing to higher analytical sensitivity of RNA ISH in tumors with low (1-2 copies per cell) to intermediate (50-100 copies per cell) HR-HPV viral copy numbers. These data support the use of RNA over DNA ISH in clinical laboratories that perform HR-HPV testing as part of their testing algorithms. [ABSTRACT FROM AUTHOR]

Angiofibroma of soft tissue (AFST) is a newly described, rare mesenchymal neoplasm with fibroblastic and vascular components; it can be seen in both sexes and in a broad age range. It presents as a slowly enlarging mass, most often in the deep tissues of the upper and lower extremities, but occasionally in a superficial location where it may be encountered by dermatopathologists. It has a benign clinical course with a very low probability of recurrence after complete excision. This lesion has a prominent vasculature and may have an infiltrative growth pattern. These features could lead to a misdiagnosis, such as malignant vascular tumor, by an unwary dermatopathologist. The diagnosis of AFST initially relied solely on morphology and immunohistochemistry but, more recently, molecular studies have begun to play a role. Because of the potential for misdiagnosis, we present this review to raise awareness. [ABSTRACT FROM AUTHOR]

Dedifferentiated liposarcoma can arise de novo or as a complication of a preexisting well-differentiated liposarcoma. We describe the radiologic and pathologic features of a long-standing liposarcoma with multiple recurrences in a 59-year-old male. Imaging demonstrated a heterogeneous fat-containing mass in the anterior thigh. The adjacent proximal femur showed irregular cortical new bone, eventually followed by intramedullary osteoblastic involvement and pathologic fracture. Histologic assessment at resection revealed dedifferentiated liposarcoma with low-grade osteosarcomatous component. The patient subsequently developed metastatic lesions in the lungs containing osteoid and osteoblastic bone metastases. We discuss the radiologic and pathologic features of this rare entity that, to our knowledge, has previously been reported to directly involve osseous structures in only one other case and discuss the potential pitfalls in diagnosis. [ABSTRACT FROM AUTHOR]

* Context.--The performance of laboratory testing has recently come under increased scrutiny as part of important and ongoing debates on regulation and reimbursement. To address this critical issue, this study compares the performance of assay methods, using either commercial kits or assays designed and implemented by single laboratories ("home brews"), including next-generation sequencing methods, on proficiency testing provided by the College of American Pathologists Molecular Oncology Committee. Objective.--To compare the performance of different assay methods on College of American Pathologists proficiency testing for variant analysis of 3 common oncology analytes: BRAF, EGFR, and KRAS. Design.--There were 6897 total responses across 35 different proficiency testing samples interrogating 13 different variants as well as wild-type sequences for BRAF, EGFR, and KRAS. Performance was analyzed by test method, kit manufacturer, variants tested, and preanalytic and postanalytic practices. Results.--Of 26 reported commercial kits, 23 achieved greater than 95% accuracy. Laboratory-developed tests with no kit specified demonstrated 96.8% or greater accuracy across all 3 analytes (1123 [96.8%] acceptable of 1160 total responses for BRAF; 848 [97.5%] acceptable of 870 total responses for EGFR; 942 [97.0%] acceptable of 971 total responses for KRAS). Next-generation sequencing platforms (summed across all analytes and 2 platforms) demonstrated 99.4% accuracy for these analytes (165 [99.4%] acceptable of 166 total next-generation sequencing responses). Slight differences in performance were noted among select commercial assays, dependent upon the particular design and specificity of the assay. Wide differences were noted in the lower limits of neoplastic cellularity laboratories accepted for testing. Conclusions.--These data demonstrate the high degree of accuracy and comparable performance across all laboratories, regardless of methodology. However, care must be taken in understanding the diagnostic specificity and reported analytic sensitivity of individual methods. [ABSTRACT FROM AUTHOR]

Cutaneous syncytial myoepithelioma (CSM) is a recently recognized, histopathological variant of myoepithelial (ME) tumors of the skin. It is characterized by a syncytial arrangement of spindled, ovoid, and/or epithelioid cells forming a well‐circumscribed, unencapsulated dermal nodule. There is a paucity of intervening stroma, and absent duct or gland formation. Strong immunohistochemical staining for S100 and epithelial membrane antigen (EMA) has been described, while cytokeratin expression has been uncommon. The majority of CSMs harbor a rearrangement involving the EWSR1 gene. Although various fusion partner genes have been discovered in ME tumors at other anatomic sites, none has yet been described in CSM. We present a case of CSM represented clinically by a papule on the mid‐upper back of a healthy 44‐year‐old female. It exhibited morphological and immunohistochemical features of a CSM with strong, diffuse S100 and alpha‐actin expression, and focal positivity for EMA and cytokeratin AE1/AE3. Fluorescence in‐situ hybridization showed an EWSR1 gene rearrangement. Massively parallel next‐generation RNA sequencing revealed PBX3 as the fusion partner. The EWSR1‐PBX3 gene fusion has been previously identified in three cases of ME tumors of bone and soft tissue, and in a case of retroperitoneal leiomyoma. This is the first report of an EWSR1‐PBX3 fusion in CSM. [ABSTRACT FROM AUTHOR]

Aims: Intraosseous hibernomas are rarely reported tumours with brown adipocytic differentiation of unknown aetiology, with only 38 cases documented in the literature. We sought to further characterise the clinicopathologic, imaging and molecular features of these tumours. Methods and result: Eighteen cases were identified occurring in eight females and 10 males (median age = 65 years, range = 7–75). Imaging indication was cancer surveillance/staging in 11 patients and clinical concern for a metastasis was raised in 13 patients. The innominate bone (7), sacrum (5), mobile spine (4), humerus (1) and femur (1) were involved. Median tumour size was 1.5 cm (range = 0.8–3.8). Tumours were sclerotic (11), mixed sclerotic and lytic (4) or occult (1). Microscopically, tumours were composed of large polygonal cells with distinct cell membranes, finely vacuolated cytoplasm, central or paracentral small bland nuclei with prominent scalloping. Growth around trabecular bone was observed. Tumour cells were immunoreactive for S100 protein (15/15) and adipophilin (5/5), while negative for keratin AE1/AE3(/PCK26) (0/14) and brachyury (0/2). Chromosomal microarray analysis, performed on four cases, did not show clinically significant copy number variation across the genome or on 11q, the site of AIP and MEN1. Conclusion: Analysis of 18 cases of intraosseous hibernoma, to our knowledge, the largest series to date, revealed that these tumours are most often detected in the spine and pelvis of older adults. Tumours were generally small, sclerotic and frequently found incidentally and can raise concern for metastasis. Whether or not these tumours are related to soft tissue hibernomas is uncertain. [ABSTRACT FROM AUTHOR]

Mesenchymal neoplasms with GLI1 alterations (rearrangements and/or amplification) have been reported recently in several anatomic locations, which include head and neck, soft tissue, and gastrointestinal tract. Herein, to the best of our knowledge, we describe the first three cases of superficial/subcutaneous mesenchymal neoplasm with GLI1 amplification. The neoplasms exhibited low‐grade cytologic features with predominant round cell morphology, glomangioma‐like areas and a rich background capillary network. There were two to three mitotic figures per 10 HPF and focal necrosis in one case. The tumors exhibited variable expression of CDK4, MDM2, STAT6, D2‐40, CD56 and cyclin D1. p16 had strong and diffuse nuclear and cytoplasmic expression in two cases. Numerous other stains were negative. Fluorescence in situ hybridization detected GLI1, DDIT3, and CDK4 coamplification in all cases, while next generation sequencing did not detect a GLI1 gene fusion. The overall features were compatible with a GLI1‐amplified mesenchymal neoplasm. In Case 1 a new distant skin lesion appeared 1 month after the surgery exhibiting similar morphology albeit with a higher mitotic index. In Cases 2 and 3, there is no evidence of local recurrence or systemic disease after 8 years and 1 month of follow‐up, respectively. These new cases of superficial GLI1‐amplified neoplasm expand its clinical spectrum and enter the realm of dermatopathology. The combination of CDK4, cyclin D1, D2‐40, and p16 expression with variable MDM2, STAT6, CD56, and S100 immunoreactivity in a low‐grade neoplasm with round/ovoid cytomorphology resembling a vascular or adnexal neoplasm may suggest the possibility of GLI1‐amplified neoplasm. [ABSTRACT FROM AUTHOR]

Context.-- Integration of molecular data into glioma classification supports diagnostic, prognostic, and therapeutic decision-making; however, testing practices for these informative biomarkers in clinical laboratories remain unclear. Objective.-- To examine the prevalence of molecular testing for clinically relevant biomarkers in adult and pediatric gliomas through review of a College of American Pathologists proficiency testing survey prior to the release of the 2021 World Health Organization Classification of Central Nervous System Tumors. Design.-- College of American Pathologists proficiency testing 2020 survey results from 96 laboratories performing molecular testing for diffuse gliomas were used to determine the use of testing for molecular biomarkers in gliomas. Results.-- The data provide perspective into the testing practices for diffuse gliomas from a broad group of clinical laboratories in 2020. More than 98% of participating laboratories perform testing for glioma biomarkers recognized as diagnostic for specific subtypes, including IDH. More than 60% of laboratories also use molecular markers to differentiate between astrocytic and oligodendroglial lineage tumors, with some laboratories providing more comprehensive analyses, including prognostic biomarkers, such as CDKN2A/B homozygous deletions. Almost all laboratories test for MGMT promoter methylation to identify patients with an increased likelihood of responding to temozolomide. Conclusions.-- These findings highlight the state of molecular testing in 2020 for the diagnosis and classification of diffuse gliomas at large academic medical centers. The findings show that comprehensive molecular testing is not universal across clinical laboratories and highlight the gaps between laboratory practices in 2020 and the recommendations in the 2021 World Health Organization Classification of Central Nervous System Tumors. [ABSTRACT FROM AUTHOR]

* Context.--Detection of acquired variants in cancer is a paradigm of precision medicine, yet little has been reported about clinical laboratory practices across a broad range of laboratories. Objective.--To use College of American Pathologists proficiency testing survey results to report on the results from surveys on next-generation sequencing-based oncology testing practices. Design.--College of American Pathologists proficiency testing survey results from more than 250 laboratories currently performing molecular oncology testing were used to determine laboratory trends in next-generation sequencing-based oncology testing. Results.--These presented data provide key information about the number of laboratories that currently offer or are planning to offer next-generation sequencing-based oncology testing. Furthermore, we present data from 60 laboratories performing next-generation sequencing-based oncology testing regarding specimen requirements and assay characteristics. The findings indicate that most laboratories are performing tumor-only targeted sequencing to detect single-nucleotide variants and small insertions and deletions, using desktop sequencers and predesigned commercial kits. Despite these trends, a diversity of approaches to testing exists. Conclusions.--This information should be useful to further inform a variety of topics, including national discussions involving clinical laboratory quality systems, regulation and oversight of next-generation sequencing-based oncology testing, and precision oncology efforts in a data-driven manner. [ABSTRACT FROM AUTHOR]

Background: Ewing sarcoma (ES) can be confirmed by identifying the EWSR1-FLI1 fusion transcript. This study is to investigate whether immunostaining (IHC) of PRKCB—a protein directly regulated by EWSR1-FLI1 is a surrogate maker for diagnosing ES in routine practice. Methods: Microarray gene expression analyses were conducted. RKCB IHC was applied to 69 ES confirmed by morphology and molecular methods, and 41 non-Ewing small round cell tumors. EWSR1 rearrangement, EWSR1-FLI1 fusion or t(11;22)(q24;q12) were identified by fluorescence in situ hybridization, reverse transcriptase polymerase chain reaction, or cytogenetic analysis, respectively. Results: Gene array analyses showed significant overexpression of the PRKCB in ES. PRKCB IHC was positive in 19 cases of ES with EWSR1-FLI1 fusion, 3 cases with cytogenetic 11:22 translocation and 59 cases with EWSR1 rearrangement while negative in only one EWSR1 rearranged case. PRKCB IHC is sensitive (98%) and specific (96%) in detecting EWSR1 rearranged ES. Conclusions: PRKCB is a reliable antibody for diagnosing ES in routine practice. [ABSTRACT FROM AUTHOR]

Background and objectives: Bone tumours are relatively rare and, as a consequence, treatment in a centre with expertise is required. Current treatment guidelines also recommend review by a specialised pathologist. Here we report on international consensus‐based datasets for the pathology reporting of biopsy and resection specimens of bone sarcomas. The datasets were produced under the auspices of the International Collaboration on Cancer Reporting (ICCR), a global alliance of major (inter‐)national pathology and cancer organisations. Methods and results: According to the ICCR's process for dataset development, an international expert panel consisting of pathologists, an oncologic orthopaedic surgeon, a medical oncologist, and a radiologist produced a set of core and noncore data items for biopsy and resection specimens based on a critical review and discussion of current evidence. All professionals involved were bone tumour experts affiliated with tertiary referral centres. Commentary was provided for each data item to explain the rationale for selecting it as a core or noncore element, its clinical relevance, and to highlight potential areas of disagreement or lack of evidence, in which case a consensus position was formulated. Following international public consultation, the documents were finalised and ratified, and the datasets, including a synoptic reporting guide, were published on the ICCR website. Conclusion: These first international datasets for bone sarcomas are intended to promote high‐quality, standardised pathology reporting. Their widespread adoption will improve the consistency of reporting, facilitate multidisciplinary communication, and enhance comparability of data, all of which will help to improve management of bone sarcoma patients. [ABSTRACT FROM AUTHOR]

Ewing sarcoma (ES) is the second most common primary bone malignancy in children and is typically characterized by a translocation involving the EWS gene on chromosome 22 and a member of the ETS family of genes: FLI1 (90%), ERG1 (5%), ETV1 (1%) , ETV4 (1%) , and FEV (1%). We identified three new cases of t(7;22) (p22;q12) ( EWS- ETV1) ES and a literature search revealed an additional six cases. In comparison to conventional ES with t(11;22) (q24;q12) ( EWS- FLI1), the t(7;22) ES variant has a higher propensity for females and children in a younger age group and it occurs more commonly in extraosseous locations. [ABSTRACT FROM AUTHOR]

Objective: To evaluate the performance of the Xpert Bladder Cancer Monitor (Xpert; Cepheid, Sunnyvale, CA, USA) test as a predictor of tumour recurrence in patients with non‐muscle‐invasive bladder cancer (NMIBC). Patients and Methods: Patients (n = 429) undergoing surveillance for NMIBC underwent Xpert, cytology, and UroVysion testing. Patients with a positive Xpert and a negative cystoscopy result (positive‐negative [PN] group, n = 66) and a control group of double negative patients (negative Xpert and cystoscopy results [NN] group) were followed for 12 months (±90 days). Results: Histology‐confirmed recurrences were detected in 58 patients (13.5%). Xpert had an overall sensitivity of 60.3% and a specificity of 76.5%. The sensitivity for high‐grade (HG) cancer was 87% with a negative predictive value (NPV) of 99%. Urine cytology showed an overall sensitivity of 23.2% (47.6% sensitivity for HG tumours) and a specificity of 88.3%. In the PN group, 32% (n = 21) developed a recurrence within 12 months, 11 of which were HG tumours. In the NN control group, 14% (n = 9) developed a recurrence and only two were HG tumours. The hazard ratio for developing recurrence in the PN group was 2.68 for all tumours and 6.84 for HG cancer. Conclusions: The Xpert test has a high sensitivity for detecting the recurrence of cancer and a high NPV for excluding HG cancer. In addition, the data suggest that patients with a positive Xpert assay in the setting of negative cystoscopy are at high risk for recurrence and need close surveillance. [ABSTRACT FROM AUTHOR]

A metastatic spindle‐cell soft‐tissue neoplasm was found to carry a novel ARHGAP23‐FER fusion. The tumor showed a rapid and sustained metabolic response to tyrosine kinase inhibitor lorlatinib. [ABSTRACT FROM AUTHOR]

Purpose: In pediatric alveolar rhabdomyosarcoma, the PAX3- FOXO1 and PAX7- FOXO1 gene fusions are prognostic indicators, while little is known concerning this disease in older patients. To determine whether PAX3/7- FOXO1 fusion gene status correlates with outcome in adolescent, young adult, and adult rhabdomyosarcoma patients, the histological, immunohistochemical, and clinical characteristics of 105 patients followed at The University of Texas MD Anderson Cancer Center from 1957 to 2001 were evaluated. Methods: The samples were assembled into a tissue microarray, and fusion gene status was determined by fluorescence in situ hybridization using PAX3, PAX7, and FOXO1 loci-specific probes. The disease characteristics and specific gene fusion were correlated with patient outcomes using the log-rank test. Results: Fifty-two percent of the samples exhibited a PAX3- FOXO1 fusion, 15% the PAX7- FOXO1 fusion, and 33% were negative for a rearrangement of these loci. The presence of PAX3/7- FOXO1 translocation was significantly associated with a higher frequency of metastatic disease. Although a statistically significant correlation between the PAX3/7- FOXO1 fusion gene status and overall survival was not identified, there was a trend toward better outcomes for patients with fusion-negative RMS. Conclusions: Therefore, identification of a FOXO1 fusion appears to be an interesting tool for predicting outcomes in older rhabdomyosarcoma patients and is worth further investigations in this rare subgroup of RMS population. [ABSTRACT FROM AUTHOR]

We report an unusual, rare case of primary epithelioid rhabdomyosarcoma of a lymph node in the parotid basin. A 72-year-old man with a history of squamous cell carcinoma of the forehead and cheek had a 5-cm mobile nontender mass of the parotid tail and right level II region. A positron emission tomography/computed tomography scan confirmed a hypermetabolic soft tissue mass in the right parotid gland. Histologic sections showed an intraparotid lymph node almost completely effaced by a centrally necrotic malignant epithelioid neoplasm consisting of uniform-appearing dyshesive cells exhibiting rhabdoid morphologic features with abundant eosinophilic fibrillary cytoplasm, eccentric nuclei, and prominent nucleoli. Bizarre cells were not seen. In immunohistochemical studies, neoplastic cells expressed desmin and myogenin. Electron microscopy showed a mixture of thick and thin filaments, primitive Z-band formation, and well-formed sarcomeres. Fluorescence in situ hybridization studies for FOXO1, PAX3, and/or PAX7 rearrangements were negative. An extensive clinical and radiologic workup showed no evidence of primary tumor elsewhere. Complete resection of the tumor was performed, and adjuvant chemotherapy was given; patient was disease free 12 months after surgery. [ABSTRACT FROM AUTHOR]

The article offers templates for pathologists to effectively report the outcomes of biomarker testing of samples from patients with melanoma. Topics covered include the use of the templates by laywers, health insurers as well as hospitals and the responsibilities of laboratories performing the biomarker testing. Also mentioned is the importance of the templates to the clinical team.