Certain undifferentiated round cell sarcomas displaying EWSR1::NFATC2 fusion have recently been reported, mostly in the bones. This report presents clinicopathological features of 3 additional EWSR1::NFATC2 fusion sarcomas of bone and soft tissues. We present 2 soft tissue and 1 bone tumors: A 62-year-old man with pain and a slowly growing, 8-cm-sized soft tissue mass in the anterolateral compartment of his right calf, along with multiple pulmonary metastatic lesions; a 63-year-old man with a 5-cm sized axillary mass of 4 months duration and a cystic renal mass; and a 53-year-old man with a complaint of leg pain was found to have a 2-cm diameter, intramedullary, lytic mass in the diaphysis of his left femur. Microscopic examination of the tumors in all patients revealed round to epithelioid cells arranged in cords and trabeculae in a myxohyaline stroma. Immunohistochemically, the tumor cells were positive for MIC2/CD99 (3/3), EMA (3/3), NKX3.1 (3/3), NKX2.2 (2/2), CD10 (2/2), and aggrecan (1/1), while negative for S100P and GFAP. Various keratins were also negative except focal AE1/AE3 positivity in the third tumor. By fluorescence in-situ hybridization, 2 tumors (#1 and #3) revealed EWSR1 gene rearrangement and amplification. Furthermore, 2 tumors (#1 and #2) displayed EWSR1ex8::NFATC2ex3 fusion with next-generation sequencing (NGS). The first patient was offered chemotherapy. However, he died of pulmonary metastasis. This report highlights the value of combining histopathological features and immunostains such as NXK3.1, NKX2.2, CD10, and aggrecan, along with EWSR1 testing for triaging these tumors for rare gene fusions by NGS that has prognostic implications.

OBJECTIVE: Cutaneous syncytial myoepithelioma (CSM) is a rare myoepithelioma variant of skin, characterized by intradermal syncytial growth of spindle cells with a distinct immunophenotype of EMA and S100 positivity and infrequent keratin expression. While CSM was first described as a cutaneous tumor, singular non-cutaneous cases have since been reported in bone. We aimed to investigate the clinicopathological features of this variant across all anatomic sites through a large multi-institutional study.
RESULTS: We complied a total of 24 myoepitheliomas with syncytial growth from our files. The tumors occurred in 12 male and 12 female patients (M:F = 1:1), with a median age of 31 years (range, 9-69 years). While the majority of tumors (75%, n = 18) occurred in skin, a significant subset (25%, n = 6) arose in non-cutaneous sites, including bone (n = 3), bronchus/trachea (n = 2), and interosseous membrane of tibia/fibula (n = 1). Tumor size ranged from 0.4 to 5.9 cm. Clinical follow-up (7 patients; range 14-202 months; median 56.5 months) showed a single local recurrence 8 years after incomplete skin excision but no metastases; all patients were alive at the time of last follow-up without evidence of disease. Histologically, all tumors were pink at low-power and characterized by a syncytial growth of bland ovoid, spindled, or histiocytoid cells with eosinophilic cytoplasm and prominent perivascular lymphoplasmacytic inflammation. One-third displayed adipocytic metaplasia (8/24). Rare cytologic atypia was seen but was not associated with increased mitotic activity. All tumors expressed S100, SMA, and/or EMA. Keratin expression was absent in most cases. Molecular analysis was performed in 16 cases, all showing EWSR1-rearrangments. In total, 15/15 (100%) harbored an EWSR1::PBX3 fusion, whereas 1 case EWSR1 FISH was the only molecular study performed.
CONCLUSIONS: Syncytial myoepithelioma is a rare but recognizable morphologic variant of myoepithelioma which may have a predilection for skin but also occurs in diverse non-cutaneous sites. Our series provides evidence supporting a reappraisal of the term \"cutaneous syncytial myoepithelioma,\" as 25% of patients in our series presented with non-cutaneous tumors; thus, we propose the term \"syncytial myoepithelioma\" to aid pathologist recognition and avoidance of potentially confusing terminology when referring to non-cutaneous examples. The behavior of syncytial myoepithelioma, whether it arises in cutaneous or non-cutaneous sites, is indolent and perhaps benign with a small capacity for local recurrence.

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Both clear cell odontogenic carcinoma (CCOC) and sclerosing odontogenic carcinoma (SOC) are rare odontogenic malignancies. Here, we report a case of maxillary CCOC whose clinical and histologic features resembled those of SOC. Radiologically, the tumor presented as an ill-defined, expansile radiolucency with local bone destruction. Histologically, the tumor was comprised of thin cords or strands of odontogenic epithelium permeating through a sclerosed fibrous stroma with occasional clear cell foci. It damaged the cortical plates and invaded the adjacent soft tissue. Immunohistochemical expression of Pancytokeratin, Cytokeratin 19, p63, Cytokeratin 5/6, and Cytokeratin 14, as well as focal expression of Cytokeratin 7, demonstrated the epithelial nature of the tumor. Alcian Blue Periodic acid Schiff staining revealed a lack of intracellular mucin. Fluorescence in situ hybridization analysis revealed Ewing sarcoma RNA binding protein 1 and activating transcription factor 1 gene translocation, further confirming the diagnosis of CCOC. Lastly, we contextualized the genetic analysis of our case to that of CCOC in the literature.

OBJECTIVE: In this study, we investigate the molecular rearrangement of EWSR1 in hyalinizing clear cell carcinoma (HCCC) (with and without eosinophilia) and clear cell variant of mucoepidermoid carcinoma (MEC) of salivary glands.
METHODS: We performed a molecular detection of HCCC (Group 1) and clear cell variant of MEC (Group 2). Group 1 consisted of 5 cases of typical HCCC and 5 cases of HCCC with eosinophilia. Group 2 encompassed 5 cases of clear-cell MEC. For both groups, we conducted a FISH analysis using EWSR1 dual color break-apart FISH probe (ZytoLight®, 22q12.2) and MAML2 dual color break-apart FISH probe (ZytoLight®, 11q21).
RESULTS: All analyzable cases of HCCC with or without eosinophilic components were negative for EWSR1 translocation. All cases of clear-cell MEC were positive for MAML2 translocation. No translocation was observed in HCCC.
CONCLUSIONS: Our study showed that clear cells could cause diagnostic uncertainty and that EWSR1 can be detected in many primary neoplasms of salivary glands and metastatic tumors that were reported in salivary glands. We suggest that recommending EWSR1 as a diagnostic molecular marker for HCCC should be reconsidered.

UNASSIGNED: Extraskeletal Ewing\'s Sarcoma (EES) may harbor more than one tumor-specific genetic abnormality, leading to diagnostic difficulties. Case report: We report a nine-year-old boy with recurrent mass of his right thigh. Tumor cells were round, with scant cytoplasm, finely dispersed chromatin, and inapparent, small nucleoli. The initial misdiagnosis was T-lymphoblastic lymphoma due to CD7 and TCR/Ig monoclonal rearrangement. As it expressed NKX2.2 and harbored an EWSR1-FLI1 fusion transcript, the diagnosis was changed to EES. The child underwent EES therapy with good initial response, but had a subcutaneous relapse at 22 months. Conclusion: In addition to typical genetic alterations, Ewing sarcoma can also express CD7 and TCR/Ig rearrangement, which are not limited to lymphoma.

Carcinomas of the thyroid with Ewing family tumor elements (CEFTEs) are small cell thyroid tumors characterized by epithelial differentiation and EWSR1-FLI1 rearrangements. In contrast to primary thyroid Ewing sarcomas, these rare tumors have a favorable prognosis. CEFTEs may co-exist with papillary thyroid carcinoma (PTC) foci and are thought to arise from either PTCs or main cells of solid cell nests (SCN). Due to their rare occurrence, characteristic clinical presentations, preoperatory sonographic (US) findings, and fine-needle aspiration (FNA) cytologic features were ill-defined until now. We report a case of a 40-year-old male who was referred to the thyroid clinic for a progressively enlarging, hard, painless, cervical mass. US examination revealed a hypoechoic nodule with lobulated margins and scant intranodular vascular signals of the right thyroid lobe. Evidence of extracapsular spread was not identified. FNA provided a Bethesda V cytology classification on conventional smears. Repeat FNA sampling with the use of a CytoFoam Core allowed a preoperative diagnosis consistent with undifferentiated thyroid carcinoma. Total thyroidectomy without lymph node dissection was performed. Histologic examination with subsequent molecular studies provided the diagnosis of papillary carcinoma of the thyroid with Ewing family tumour elements (CEFTEs). No additional treatment was rendered and the patient showed no evidence of local or distant disease by clinical examination, US, and 18FDG-TAC/PET after 6 months of follow-up. This is the first reported case of CEFTE with complete clinical, US, cytologic, and immunohistochemical preoperatory assessment.

Hyalinizing clear cell carcinoma (HCCC) is an uncommon low-grade minor salivary gland neoplasm that usually arises in the head and neck region. We report a 55-year-old man who presented with a 2.5 cm lung mass that was partially obstructing the right bronchus intermedius. The tumor consisted of cords and nests of clear and eosinophilic cells in a hyalinized stromal background. The neoplastic cells expressed cytokeratin (CK) 7, CK 5/6, high-molecular weight cytokeratin (34BE12), p63 and p40, while TTF-1, napsin A, CK20, S100, smooth muscle actin, synaptophysin and chromogranin were negative. Mucicarmine stain also was negative in the lesional cells. Fluorescence in situ hybridization using break apart probes revealed rearrangement of the Ewing Sarcoma Breakpoint Region 1 gene locus. The morphologic, immunophenotypic and cytogenetic findings confirmed the diagnosis of HCCC, most likely of bronchial submucosal gland origin. To our knowledge, only two other reports of primary pulmonary HCCC are available in English literature.

Myoepitheliomas of soft tissue are rare tumors with variable morphologic, immunohistochemical and molecular profiles and therefore are diagnostically challenging for pathologists. We report a case in a 60-year-old male with a painless slowly growing 3cm mass on left medial forefoot. Core biopsy of the mass showed a neoplastic proliferation of plasmacytoid tumor cells, consistent with myoepithelioma of soft tissue. Immunohistochemical stains demonstrated positivity of the tumor cells for cytokeratin AE1/AE3, CK18, S-100 protein and myosin heavy chain (SMMS-1), supporting the diagnosis. Fine-needle aspiration was performed intraoperatively before the resection of the mass. Air-dried Diff-Quik stained cytology slides showed singly scattered and loosely cohesive clusters of plasmacytoid and spindle cells with dense basophilic cytoplasm, distinct cytoplasmic borders, and round to oval mildly pleomorphic nuclei with smooth nuclear membrane. Scattered naked nuclei, binucleated tumor cells, as well as tumor cells with wispy elongated cytoplasm were also seen. Occasional clusters of cells were intimately associated with metachromatic fibrillary stromal material. Histologic examination of the resected tumor confirmed the diagnosis of myoepithelioma. Molecular studies showed absence of EWSR1 rearrangement. Cytological differential diagnosis, clinical, histological, immunohistochemical, and molecular features of soft tissue myoepitheliomas are discussed in this study.

Carcinomas of the thyroid with Ewing family tumor element (CEFTEs) are small-cell thyroid tumors with epithelial differentiation that disclose p63 expression and EWSR1-FLI1 rearrangement, carry a favorable prognosis and may co-exist with papillary thyroid carcinoma (PTC) foci. Two histogenetic hypotheses have been advanced regarding the origin of CEFTEs: arising in PTCs or in solid cell nests (SCN). A total of 3 CEFTEs, 54 PTCs, and 10 SCNs were reviewed, and fluorescence in situ hybridization (FISH) technique was performed in all cases to search for the presence of EWSR1 rearrangements. The three CEFTEs disclosed the EWSR1-FLI1 rearrangement both in the small cell and in the PTC component. Out of the 54 PTC cases, 28 (51.9%) were positive, 20 (37.0%) were negative, and 6 (11.1%) were inconclusive for EWSR1 rearrangement; in two of the positive PTC cases, the EWSR1-FLI1 rearrangement was detected. Classic PTC disclosed more often the EWSR1 rearrangement than other PTC variants (p = 0.031). PTCs with EWSR1 rearrangement disclosed a lower percentage of nuclei with EWSR1 polysomy than those without EWSR1 rearrangement (p = 0.001). Out of the 10 SCNs, 7 (70.0%) were negative and 3 (30.0%) were inconclusive for the EWSR1 rearrangement. Monosomic nuclei were more frequent (mean of 44.3%) in SCNs than in PTCs (p < 0.001). The presence of the EWSR1-FLI1 rearrangement in PTC component of all studied CEFTEs and the existence of the EWSR1 rearrangement in some PTCs favor the origin of CEFTE from PTC. The high frequency of EWSR1 rearrangements in PTC may represent a new diagnostic marker of these tumors.