Myoepithelial Tumors Research Articles

Retroperitoneal Myoepithelial Carcinoma with Heterologous Bone Formation and EWSR1::ZNF444

Abstract Introduction/Objective Soft tissue myoepithelial tumors are rare tumors that affect a wide age range and diverse tissue sites. Fewer than five cases have been reported in the retroperitoneum. Most tumors are benign with the only histologic criterion for malignancy being cytologic atypia. The morphology is broad ranging from spindled to epithelioid cells of varying cellularity in sclerotic to myxoid stroma. Heterologous differentiation may be present. These tumors usually express cytokeratin, EMA, S100, and GFAP and show EWSR1 and FUS rearrangements. Here we present an unusual case of retroperitoneal myoepithelial carcinoma. Methods/Case Report A 29-year-old female presented with rash and painless jaundice. CT and MRCP revealed a relatively circumscribed 3.7 cm mass in the porta hepatis. On fine needle aspiration, a possible gastrointestinal stromal tumor was considered due to DOG1 expression. The patient underwent a Whipple procedure with negative margins showing tumor in soft tissue adjacent to the common bile duct. The tumor was multinodular and consisted predominantly of mild to moderately pleomorphic epithelioid cells in fibromyxoid stroma with interspersed woven bone. Mitoses were not appreciated, and necrosis not seen. The tumor was focally positive for CK AE1/AE3, GFAP, and DOG1 and negative for S100, SOX10, p63, and CD117. INI1 was retained. NGS identified EWSR1::ZNF44 and a diagnosis of myoepithelial carcinoma was rendered. The patient received no adjuvant therapy and has not shown any evidence of metastasis or recurrence for 17 months. Results (if a Case Study enter NA) NA Conclusion Soft tissue myoepithelial carcinomas are aggressive tumors with approximately 40% recurrence and over 50% metastasis. Standard treatment is complete surgical resection. The efficacy of radiation and chemotherapy is not clear. EWSR1 fusions with various partners including POU5F1, PBX1/3, and ZNF44 have been identified. Due to their rarity and varying histology and immunohistochemical expression, identification of gene fusions can be invaluable in diagnosing soft tissue myoepithelial tumors, especially in unusual locations.

Expanding the Molecular Spectrum of Carcinoma Ex Pleomorphic Adenoma: An Analysis of 84 Cases With a Novel HMGA2::LINC02389 Fusion.

Carcinoma ex pleomorphic adenoma (CXPA) is an aggressive epithelial and/or myoepithelial neoplasm that arises in association with a pleomorphic adenoma (PA). Its etiopathogenesis remains poorly understood, but it is believed that the development of this tumor is due to the accumulation of genetic, protein, metabolic, and epigenetic alterations in a PA. A retrospective review of the Salivary Gland Tumor Registry in Pilsen yielded 84 CXPA, namely 25/84 salivary duct carcinoma (SDC), 15/84 myoepithelial carcinoma (MC), 1/84 epithelial-myoepithelial carcinoma (EMC), and 1/84 adenoid cystic carcinoma (AdCC). All 84 CXPA cases were analyzed by next-generation sequencing (NGS) and/or fluorescence in situ hybridization (FISH). Forty-three tumors originally diagnosed as CXPA (43/84, 51.2%) showed some molecular alteration. Fusion transcripts were identified in 12/16 (75%) CXPA, including LIFR::PLAG1, CTNNB1::PLAG1, FGFR1::PLAG1, and a novel fusion, HMGA2::LINC02389. Most of the fusions were confirmed by FISH using PLAG1 (6/11) and HMGA2 (1/1) gene break probes. Split signals indicating gene break were identified by FISH for PLAG1 (12/17), HMGA2 (3/4), EWSR1 (7/22), and MYB (2/7). Concerning pathogenic mutations, only CXPA with epithelial differentiation (SDC) presented these alterations, including HRAS mutation (2/4), TP53 (1/4), PTEN (1/4), and ATK1 (1/4). In addition, amplifications in ERBB2 (17/35), MDM2 (1/4), and EWSR1 (1/7) were detected. A novel finding was the discovery of an HMGA2::LINC02389 fusion in 1 patient with EMC ex-PA. The present results indicate that molecular profiling of CXPA with myoepithelial differentiation (MC) tends to reveal chromosomal fusion events, whereas CXPA with epithelial differentiation (SDC) tends to have a higher frequency of pathogenic mutations and gene amplifications.

Myoepithelial Carcinoma arising from a Parotid Pleomorphic Adenoma A Case Report

Myoepithelial carcinoma is a rare neoplasm, accounting for less than 2% of all salivary gland carcinomas and can arise de novo or secondary to a previous pleomorphic adenoma, as in the case presented here. The presence of mitoses, foci of necrosis, characteristic histomorphology, and exclusive proliferation of myoepithelial cells identified by immunohistochemistry confirm the diagnosis. The gold standard of therapy is surgical resection with clear margins; however, the risks of local recurrence and distant metastasis are 35% and 22%, respectively. Our case corresponds to a 65-year-old patient who underwent surgery for a pleomorphic adenoma, which recurred after 5 years. She presented to our clinic with a myoepithelial tumor of 2 months’ evolution with involvement of the facial nerve and soft tissues. Due to its rapid growth, this is an unusual presentation.

A Clinicopathological Study of Parotid Gland Tumours

Abstract Background: The parotid gland is the largest salivary gland. Pleomorphic adenoma (PA) is the most common tumour found in the parotid gland. Most of the parotid tumours are painless and slow-growing. Ultrasound, computed tomography and magnetic resonance imaging are modalities of diagnosis. Fine-needle aspiration cytology (FNAC) is done in some cases, and its use is controversial. Aim: This clinicopathological study mainly aims at the demographic profile of the patient and clinical implications. Investigations were done and also evaluating the efficacy of FNAC in diagnosing parotid gland tumours. Materials and Methods: We conducted a prospective, hospital-based, observational study at our institution from December 2020 to June 2022. Forty patients who satisfied the inclusion and exclusion criteria were enrolled in the study. The study was analysed using SPSS version 25 developed by IBM. The categorical variables were presented as frequency and continuous data as mean, standard deviation (SD) and range with confidence interval. Categorical variables were compared using the Chi-square test; P <0.05 is considered significant. The sensitivity, specificity positive predictive value (PPV) and diagnostic accuracy of FNAC against the gold-standard histopathological examination (HPE) were worked out. The results are shown in tabular and graphical format. Results: The incidence of swelling was higher in males than females. Swelling was the most common clinical feature of the parotid gland. The duration of the disease ranges from ½to 48 months with an SD of 8.26 and a 95% confidence interval. One patient presented with facial nerve involvement and one patient presented with lymph node involvement. Five patients gave a history of surgery done in the past, which indicates recurrence, 10 (25%) patients were smokers and 1 (3%) patient had a history of previous radiation. Amongst the population of smokers, Warthin’s tumours were the most common (50%), PA (20%), oncocytic lipoadenoma, mucoepidermoid (MEP) carcinoma and myoepithelial (MyoEP) tumours having 10% incidence. The radiological findings were evaluated showing PA in 72.5% of cases, Warthin’s in 7.5%, neoplasm in 7.5% and non-specific cyst parotitis in 2.5% each. One patient image shows features of malignancy. FNAC says that 67.5% were PA, 20% were Warthin’s cyst and non-specific cyst, MEP and inflammation, but in one patient, FNAC was inconclusive. Most of the study population underwent superficial parotidectomy (32.5%); 30% of the study group underwent superficial conservative parotidectomy, but 27.5% of patients underwent total conservative parotidectomy. About 2.5% of the study group underwent extracapsular excision and enucleation. However, 2 (5%) patients were done with simple excision only. After surgery, out of 40, 38 patients had neuropraxia which recovered on follow-up. The most common tumour was PA (67.5%), and Warthin’s (22.5%) malignant tumours like MEP and MyoEP were 5% and 2.5%, respectively. Rare benign tumours like oncocytic lipoadenoma were the finding of HPE in FNAC that was inconclusive in this case. The incidence of malignant tumours was more common in males than in females, and it was more common in the age group of 21–40 years. MEP carcinoma was the most common malignant tumour. The efficacy of FNAC was identified in terms of sensitivity, specificity, negative predictive value (NPV), PPV and diagnostic accuracy. The sensitivity for benign tumours was 91.89% and that for malignant tumours was 33.33%. The specificity was 33.33% for benign tumours and 100% for malignant tumours respectively. The PPV was 94.44% for benign and 100% for malignant tumours. NPV was 25% and 94.87%, respectively. The diagnostic accuracy was 87.5% and 95%. Conclusion: Although FNAC has some pitfalls, the high sensitivity, specificity and accuracy in diagnosing malignant lesions as evident from this study indicate that FNAC is a reliable diagnostic method when correctly performed and interpreted by an experienced cytopathologist. Not all parotid lesions are lumps are malignant. Most of the masses are benign in nature. FNAC is a simple, safe, painless and cost-effective method for easy diagnosis.

Benign Myoepithelial Neoplasms of Salivary Glands, Clinicopathologic Features and Review of the Literature

Benign Myoepithelial Neoplasms of Salivary Glands, Clinicopathologic Features and Review of the Literature

Myoepithelial tumors of soft tissue and bone in children and young adults: A clinicopathologic study of 40 cases occurring in patients ≤ 21 Years of age

Myoepithelial tumors of the soft tissue and bone occurring in patients 21 years of age and younger are rare, and their clinicopathologic features remain incompletely understood. We studied a well-characterized series of 40 such tumors. Cases were retrieved from our archives for the period 2009–2022 and re-reviewed. Available immunohistochemical and molecular genetic data was collected. Clinical information including available follow-up was obtained. The tumors occurred in 18 males and 22 females, ranging from 3 months to 21 years of age (median 11.5 years), and involved a wide variety of soft tissue (n = 36) and bone (n = 4) locations. Histologically benign myoepithelial tumors tended to occur in adolescents (median age 14.5 years; range 5–21 years), whereas myoepithelial carcinomas occurred in younger patients (median age 8.5 years; range 3 months–20 years). Microscopically, the tumors showed a complex admixture of epithelioid, plasmacytoid and spindled cells in a variably hyalinized, myxoid, chondroid or chondromyxoid background. Small subsets of histologically malignant tumors had rhabdoid or “round cell” features. Immunohistochemistry showed 35/40 (88%) cases to be positive with at least one keratin antibody. The 5 keratin-negative tumors were uniformly positive for S100 protein and/or SOX10 and expressed EMA (4 cases) and/or p63 (3 cases). EMA, SMA and GFAP were positive in 21/25 (84%), 13/21 (62%), and 8/21 (38%) tumors, respectively. SMARCB1 and SMARCA4 expression was retained in 29/31 (94%) and 22/22 (100%) of cases, respectively. FISH for EWSR1 gene rearrangement was positive in 6/18 (33%) tested cases. Two EWSR1-negative tumors were also FUS-negative. NGS identified EWSR1::POU5F1, FUS::KLF17, and BRD4::CITED1 gene fusions in 3 tested cases. Clinical follow-up (22 patients; median 23 months; range 1–119 months) showed 3 patients with local recurrences and 5 with distant metastases (lymph nodes, lung, and brain). Three patients died of disease, 3 were alive with recurrent or unresectable disease, and 16 were disease-free. Adverse clinical outcomes were seen only in patients with malignant tumors. We conclude that myoepithelial neoplasms of soft tissue and bone are over-repesented in patients ≤21 years of age, more often histologically malignant, and potentially lethal. Histologic evaluation appears to reliably predict the behavior of these rare tumors.

Myoepithelial Tumors of Bone With EWSR1::PBX3 Fusion: A Spectrum From Benign to Malignant

The EWSR1::PBX3 fusion gene, commonly associated with cutaneous syncytial myoepitheliomas, is also found in myoepithelial tumors (METs) of bone and soft tissue. These tumors typically demonstrate benign histology and favorable outcomes. This study examines 6 previously unreported intraosseous METs harboring the EWSR1::PBX3 fusion, focusing on their histopathologic characteristics, immunophenotype, clinical and radiographic profiles, and patient outcomes. The cohort comprised 5 men and 1 woman, aged 25 to 65 years (median age: 31 years), with tumors located in the proximal tibia (3 cases), distal radius (2 cases), and ilium (1 case) and sizes between 3.2 and 12.2 cm (median size: 3.9 cm). Imaging showed osteolytic lesions with varying degrees of cortical involvement and soft tissue extension in 3 cases. Histologically, 4 tumors showed mainly uniform oval-to-spindled cells in syncytial or fascicular arrangements within a collagenous matrix, displaying either bland nuclear features or mild atypia, and low to slightly elevated mitotic activity (≤1 per 10 high-power fields in 3 cases and 6 per 10 high-power fields in 1), classifying them as benign or atypical METs. In contrast, 2 tumors exhibited pronounced nuclear atypia with ovoid, spindled, epithelioid and round cells, hyperchromatic nuclei, inconspicuous nucleoli, increased N/C ratios, high mitotic rates (17 and 19 per 10 high-power fields), and extensive necrosis. Both tumors behaved aggressively—one patient underwent amputation after neoadjuvant chemotherapy and radiation, and the other died within 7 months with the disease still present. Immunohistochemically, the tumors consistently expressed epithelial membrane antigen and S100 but lacked keratin (AE1/AE3) expression. Our study demonstrated that bone METs with EWSR1::PBX3 fusions encompass a histologic continuum from benign to malignant, with benign/atypical METs mirroring their cutaneous analogs in morphology, and malignant variants distinguished by heterogeneous cytologic and architectural features, pronounced nuclear atypia, and high mitotic rates.

Molecular analysis of apocrine mixed tumors and cutaneous myoepitheliomas: a comparative study confirming a continuous spectrum of one entity with near-ubiquitous PLAG1 and rare mutually exclusive HMGA2 gene rearrangements.

Myoepithelial neoplasms of the skin and soft tissue still represent a confusing and somewhat controversial field in pathology as it appears that this category includes several different entities. However, recent studies have suggested that both apocrine mixed tumors (AMT) and cutaneous myoepitheliomas (CM) harbor identical chromosomal rearrangements involving the PLAG1 gene and hence may represent a morphological spectrum. The aim of the present study was to share our institutional experience with these tumors and specifically focus on studying their immunohistochemical and molecular features to further assess their relatedness. Eleven cases of AMT and 7 cases of CM were collected and analyzed using immunohistochemistry (IHC), PLAG1 FISH, and Archer FusionPlex assay. There were 14 male and 4 female patients with ages ranging from 26 to 85 years (median 55.8 years, mean 58.5 years). AMTs were mainly located in the head and neck (n = 10), while CMs were mainly located in the acral sites (n = 5). PLAG1 IHC was diffusely strongly positive in 14/17 (82%) cases, whereas a single case of AMT diffusely expressed HMGA2. Both tumor groups showed PLAG1 gene fusions which were detected in 6/13 analyzable samples (AMT, n = 4 and CM, n = 2), and included TRPS1::PLAG1 (n = 3), NDRG1::PLAG1 (n = 1), CTNNB1::PLAG1 (n = 1) and a novel PXDNL::PLAG1 fusion (n = 1). The remaining 5 cases were negative, 5 were not analyzable and the single case positive for HMGA2 by IHC revealed a potential HMGA2 gene rearrangement. The cases were further studied by FISH, with 12/17 cases showing PLAG1 gene rearrangement (AMT, n = 8 and CM, n = 4). Altogether, 14/18 cases showed PLAG1 gene rearrangement by at least one of the methods. PLAG1 immunohistochemistry had a 92% specificity and sensitivity. Our study provided additional data to suggest that AMT and CM share overlapping morphological and immunohistochemical features as well as molecular background characterized by PLAG1 gene fusions and thus represent a morphological spectrum. In addition, we identified a novel PXDNL::PLAG1 fusion and suggested that rare cases may harbor HMGA2 gene alterations which seem to be mutually exclusive with PLAG1 gene fusions. The relatedness of these tumors to salivary gland myoepithelial neoplasms and distinctness from eccrine mixed tumors and other skin and soft tissue myoepithelial neoplasms with EWSR1/FUS fusions is discussed.

PLAG1 Rearranged Soft Tissue Tumor in an Adult

Abstract Introduction/Objective PLAG1 rearranged soft tissue tumor is a recently described entity in the pediatric population. Less than 10 cases have been reported identifying PLAG1 gene fusions with various gene partners. This tumor is characterized by spindled cells with low cellularity in fibromyxoid stroma, expressing CD34 and desmin. PLAG1 gene fusions have been identified in various other tumors, including lipoblastoma, salivary gland pleomorphic adenoma, myoepithelial tumors, uterine epithelioid and myxoid leiomyosarcomas, and chondroid syringoma. To our knowledge, we report the first case of a PLAG1 rearranged soft tissue tumor in an adult. Methods/Case Report A 32-year-old female with no significant medical history presented with a left thigh mass. MRI showed a 9.8 cm mass involving subcutaneous fat and causing marked sartorius muscle displacement. Resection showed a well-circumscribed, spindle cell tumor of low cellularity in a myxo-collagenous stroma. Bland, elongated, and ovoid-shaped spindled cells with occasional punctate nucleoli were seen. No mitoses or necrosis were identified. The tumor cells expressed CD34 and androgen receptors, partially expressed desmin and estrogen receptors, and focally expressed S100. MUC4 and beta-catenin were negative. Next-generation sequencing performed at Mayo Clinic Labs identified UBC::PLAG1 gene rearrangement. Results (if a Case Study enter NA) NA Conclusion To our knowledge, we describe the first case of PLAG1 rearranged soft tissue tumor in an adult. This case is also unique as the fusion partner gene, UBC, was not previously identified. All other cases reported occurred in those four years of age or younger, with one report in a 15-year-old female. Our patient has had less than six months of follow-up with no recurrence. With few cases reported, and relatively short follow-up periods thus far, the behavior of these tumors remains undetermined.

SMARCB1/INI1-deficient epithelioid and myxoid neoplasms in paratesticular region: Expanding the clinicopathologic and molecular spectrum

SMARCB1/INI1-deficient soft tissue tumors with epithelioid and myxoid features are diverse and mainly include soft tissue myoepithelial tumor, extraskeletal myxoid chondrosarcoma, and the recently described myoepithelioma-like tumor of the vulvar region and myxoepithelioid tumor with chordoid features. Because of their overlapping features, the accurate diagnosis and classification of these tumors are often challenging. Herein, we report two unique cases of SMARCB1/INI1-deficient soft tissue neoplasm with epithelioid and myxoid features occurring in male paratesticular region. The first case was a 52-year-old man presented with an intermittent painful left paratesticular mass for 1 year. The second case was a 41-year-old man presented with a painless paratesticular mass on the right side for 3 months. Both patients underwent an orchiectomy. After 6 and 26 months of follow-up, both were alive with no evidence of recurrence or metastasis. In both cases, the tumor was relatively well-demarcated and showed monomorphic round to epithelioid cells arranged in a nested, trabecular, reticular, and corded pattern, setting in a myxohyalinized and vascularized matrix. The tumor cells showed relatively uniform round nuclei with vesicular chromatin and variably prominent nucleoli. No rhabdoid cells were identified. Mitoses numbered 3 and 2 per 10 high-power fields. Tumor necrosis or lymphovascular invasion was absent. Immunohistochemically, both tumors expressed epithelial membrane antigen (focal), calponin (focal), and CD99. SMARCB1/INI1 expression was deficient in both cases. In addition, case 1 diffusely expressed pan-cytokeratin, and case 2 diffusely expressed CD34 and synaptophysin. Molecular genetically, case 1 showed SMARCB1 homozygous deletion as detected by fluorescence in-situ hybridization (FISH), and case 2 demonstrated SMARCB1 copy number deletions by next-generation sequencing and SMARCB1 monoallelic deletion by FISH. Both cases lacked EWSR1 rearrangements by FISH. The overall clinicopathologic profiles of the two cases made it difficult to classify them as one of the established categories of SMARCB1/INI1-deficient mesenchymal tumors. Our study further expands the clinicopathologic and molecular spectrum of SMARCB1/INI1-deficient epithelioid and myxoid neoplasms and highlights the challenges to diagnose these tumors.

Single-cell transcriptomic analysis uncovers the origin and intratumoral heterogeneity of parotid pleomorphic adenoma

Pleomorphic adenoma (PA) is the most common benign tumour in the salivary gland and has high morphological complexity. However, the origin and intratumoral heterogeneity of PA are largely unknown. Here, we constructed a comprehensive atlas of PA at single-cell resolution and showed that PA exhibited five tumour subpopulations, three recapitulating the epithelial states of the normal parotid gland, and two PA-specific epithelial cell (PASE) populations unique to tumours. Then, six subgroups of PASE cells were identified, which varied in epithelium, bone, immune, metabolism, stemness and cell cycle signatures. Moreover, we revealed that CD36+ myoepithelial cells were the tumour-initiating cells (TICs) in PA, and were dominated by the PI3K-AKT pathway. Targeting the PI3K-AKT pathway significantly inhibited CD36+ myoepithelial cell-derived tumour spheres and the growth of PA organoids. Our results provide new insights into the diversity and origin of PA, offering an important clinical implication for targeting the PI3K-AKT signalling pathway in PA treatment.

Primary cutaneous myoepithelial carcinoma A report of two cases with literature review

Myoepithelial tumors encompass a spectrum of neoplasms demonstrating myoepithelial differentiation. While originally well-described in salivary glands, these tumors have been increasingly reported in bone, soft tissue, and cutaneous tissues 1.

Superficial mesenchymal tumours expressing epithelial markers on immunohistochemistry: Diagnostic clues and pitfalls.

The diagnosis of mesenchymal neoplasms arising in the superficial soft tissue can be challenging as some entities are rare and show overlapping features. Moreover, the spectrum of mesenchymal tumours has expanded recently to include potential new entities, some of which have been described after the 5th edition of the World Health Organisation (WHO) classification of soft tissue and bone tumours published in 2020. In the skin and superficial soft tissue, tumours of epidermal, melanocytic and appendageal origin are more commonly encountered than mesenchymal neoplasms. However, specific entities from the latter category can occasionally express epithelial markers on immunohistochemistry, some of them in a strong and diffuse manner. It is therefore crucial to be aware of diagnostic pitfalls when encountering cytokeratin positivity in superficial soft tissue neoplasms. This article provides an overview on the differential diagnosis of these mesenchymal tumours that can sporadically occur also in the skin, including myoepithelial neoplasms, epithelioid sarcoma, keratin positive giant cell tumour of soft tissue / xanthogranulomatous epithelial tumour, superficial CD34-positive fibroblastic tumour / PRDM10-rearranged soft tissue tumour, and perineurioma.

Cytopathology of salivary gland myoepithelial carcinoma: A study of 13 cases and review of the literature

Myoepithelial carcinoma (MECA) is an infrequently recognized salivary gland (SG) neoplasm that commonly develops within a preexisting pleomorphic adenoma (MECA ex PA). Fine-needle aspiration (FNA) biopsy reports of this neoplasm are largely restricted to small series and single case reports. Our cytopathology files were searched for examples of SG MECA/MECA ex PA having confirmatory histopathologic verification. Conventional FNA biopsy smears were performed, and exfoliative specimens processed using standard techniques. Thirteen cases from 9 patients (M:F = 3.5:1; age range: 36 to 95 years, mean age = 60 years) met inclusion criteria. FNA biopsy sites included parotid gland (4), trunk (2), scalp (2), and neck (2). Exfoliative specimens included pleural fluid (1), bronchial brushing (1), and bronchoalveolar lavage (1). Most cases were metastatic deposits (8; 62%), 4 were primary neoplasms, and 1 a local recurrence. FNA diagnoses were MECA ex PA (6; 46%), myoepithelial neoplasm (2), PA (2), basaloid neoplasm (1), atypical myoepithelial cells (1), and myxoma (1). Ancillary testing in 2 cases showed positive staining for myoepithelial markers. Cytologic features were that of a low-grade neoplasm composed principally of epithelioid/polygonal cells exhibiting minimal if any cytologic atypia. Myxoid and chondromyxoid stroma was often the dominant feature in MECA ex PA aspirates. In the primary setting, a cytologic diagnosis of MECA/MECA ex PA is extremely challenging if at all possible. Due to overwhelming amounts of stroma, the diagnosis may be challenging in some cases of metastatic MECA ex PA.

TAF15::NR4A3 gene fusion identifies a morphologically distinct subset of extraskeletal myxoid chondrosarcoma mimicking myoepithelial tumors.

Extraskeletal myxoid chondrosarcoma (EMC) is a rare sarcoma of uncertain differentiation predominantly arising in deep soft tissue. Its conventional morphologic appearance manifests as a relatively well-circumscribed, multilobular tumor composed of uniform short spindle-to-ovoid primitive mesenchymal cells with deeply eosinophilic cytoplasm arranged in anastomosing cords within abundant myxoid matrix. The genetic hallmark of EMC has long been considered to be pathognomonic gene rearrangements involving NR4A3, which when fused to TAF15, often have high-grade morphology with increased cellularity, moderate to severe cytologic atypia, and rhabdoid cytomorphology. Herein, we describe two cases of EMC with TAF15::NR4A3 fusion that appear morphologically distinct from both conventional and high-grade EMC. Both cases had an unusual biphasic appearance and showed diffuse positivity for p63, mimicking myoepithelial tumors. DNA methylation profiling demonstrated that both cases clearly cluster with EMC, indicating that they most likely represent morphologically distinct variants of EMC. The clinical significance and prognostic impact of this morphologic variance remains to be determined. Molecular testing, including DNA methylation profiling, can help to confirm the diagnosis and avoid confusion with mimics; it adds another layer of data to support expanding the morphologic spectrum of EMC.

The extracellular matrix landscape in salivary gland carcinomas is defined by cellular differentiation via expression of three distinct protein modules.

The extracellular matrix (ECM) is an integral part of the tumor microenvironment of carcinomas. Even though salivary gland carcinomas (SGCs) display a range of tumor cell differentiation and distinct extracellular matrices, their ECM landscape has not been characterized in depth. The ECM composition of 89 SGC primaries, 14 metastases, and 25 normal salivary gland tissues was assessed using deep proteomic profiling. Machine learning algorithms and network analysis were used to detect tumor groups and protein modules that explain specific ECM landscapes. Multimodal in situ studies to validate exploratory findings and to infer a putative cellular origin of ECM components were applied. We revealed two fundamental SGC ECM classes which align with the presence or absence of myoepithelial tumor differentiation. We describe the SGC ECM through three biologically distinct protein modules that are differentially expressed across ECM classes and cell types. The modules have a distinct prognostic impact on different SGC types. Since targeted therapy is rarely available for SGC, we used the proteomic expression profile to identify putative therapeutic targets. In summary, we provide the first extensive inventory of ECM components in SGC, a difficult-to-treat disease that encompasses tumors with distinct cellular differentiation. © 2023 The Authors. The Journal of Pathology published by John Wiley & Sons Ltd on behalf of The Pathological Society of Great Britain and Ireland.

Myoepithelioma, myoepithelioma-like, and chondroid soft-tissue tumors arising at acral sites: a review

Myoepithelial neoplasms comprise a histologically and immunophenotypically diverse spectrum of entities. The following review is a comprehensive summary of acral lesions demonstrating myoepithelial-like and chondroid histomorphology, as well as recently described mimics that are diagnostically challenging to distinguish. The salient clinicopathologic, immunophenotypic, and molecular features of each entity are described.

Top Ten Differentials to Mull Over for Head and Neck Myoepithelial Neoplasms.

Myoepithelial neoplasms of the salivary gland are benign or malignant neoplasms composed exclusively of neoplastic myoepithelial cells. These tumors, including the benign myoepithelioma and the malignant counterpart myoepithelial carcinoma, exhibit a wide range of cytomorphologic features and architectural patterns. Review. Myoepithelial cells can be epithelial, plasmacytoid, clear cell, spindle cell, and/or oncocytic cell, arranging as trabeculae, solid sheets, nests, cords, and/or single cells. A stromal component is commonly but not universally present, Therefore, their differential diagnoses are quite broad, including salivary gland neoplasms especially those with a myoepithelial component, plasmacytoma, melanoma, and various mesenchymal tumors. In this review, we summarize the characteristic histologic features, useful immunohistochemical panel, and common molecular alterations of myoepithelial tumors and their top differential diagnoses. A logical stepwise algorithmic approach and an immunohistochemical panel to include multiple myoepithelial markers are essential to establish the correct diagnosis.

Tumeurs myoépithéliales des tissus mous : à propos d’un cas de tumeur mixte

Myoepithelial neoplasms of soft tissue represent a rare entity which has been described only recently when compared to salivary gland tumors with whom they share histopathological and molecular features. The most common locations are the superficial soft tissues of the limbs and limb girdles. However, they can rarely occur in the mediastinum, abdomen, bone, skin and visceral organs. Benign forms (myoepithelioma and mixed tumor) are more frequent than myoepithelial carcinoma and the latter mostly affects children and young adults. Diagnosis is mainly based on histology, which shows a proliferation of myoepithelial cells of variable morphology with or without glandular structures in a myxoid background, and immunohistochemistry, which shows co-expression of epithelial and myoepithelial markers. Molecular tests are not mandatory, but in selected cases FISH analysis can prove useful as about 50% of myoepitheliomas show EWSR1 (or rarely FUS) rearrangements and mixed tumors show PLAG1 rearrangements. Here, we present a case of a mixed tumor of the soft tissue occuring in the hand with expression of PLAG1 in immunohistochemistry.

Keratin-positive fibrotic extraskeletal myxoid chondrosarcoma: a close mimic of myoepithelial tumour.

Extraskeletal myxoid chondrosarcoma (EMC) is a rare form of adult sarcoma with distinct histology and NR4A3 gene fusion. Immunohistochemically, EMCs are variably positive for S100 protein and neuroendocrine markers. Unlike histologically similar soft-tissue myoepithelial tumours, keratin expression is rare. Prompted by two recent EMC cases with diffuse keratin expression, we investigated the expression of epithelial markers in a molecularly confirmed cohort of EMC and identified two additional similar cases. Four keratin-positive EMCs occurred in one man and three women aged 46-59 years. All tumours displayed nonclassic histology with prominent stromal fibrosis, and keratin AE1/AE3 was expressed either diffusely (N=2) or focally (N=2). In one tumour, keratin expression was limited to the sclerotic area. All tumours coexpressed epithelial membrane antigen and two additionally expressed S100 protein or glial fibrillary acidic protein. All tumours harboured NR4A3 fusions, including TAF15::NR4A3 (N=1) and EWSR1::NR4A3 (N=3). Two cases were initially considered as most consistent with myoepithelial tumours based on widespread stromal fibrosis and keratin expression. DNA methylation analysis classified two tumours tested as EMCs. We identified a small subset of EMCs characterised by keratin expression and prominent stromal fibrosis. This histological pattern must be recognised in the differential diagnosis of myoepithelial tumours because misclassification may lead to the erroneous prediction of tumour behaviour and may alter patient management. NR4A3 genetic analysis should be considered even in the face of keratin expression and prominent stromal fibrosis.