Soft tissue myoepithelial carcinoma with rhabdoid‐like features and EWSR1 rearrangement: Fine needle aspiration cytology with histologic correlation

Abstract

A new case of soft tissue myoepithelial carcinoma (MEC) with rhabdoid-like differentiation is presented including cytologic, histopathologic, immunohistochemical, and molecular biologic features. A 45-year-old woman was admitted to the Hospital with nodular mass involving the lower part of the abdominal wall. Fine-needle aspiration cytology showed a round cell tumor with abundant cytoplasm in the myxoid background. The nuclei were uniform, round to ovoid, with finely distributed chromatin, nucleoli, and pale, vacuolated, or eosinophilic cytoplasm with rhabdoid-like appearance resembling a soft tissue malignant rhabdoid tumor. The surgically removed tumor was poorly demarcated, yellow, soft, and myxoid. The histopathology revealed sheets of poorly differentiated round malignant cells with focal myxoid stroma and rhabdoid-like morphology. Immunohistochemistry showed positivity for CK (AE1/AE3), EMA, S100, vimentin, CD99, and SMA; however desmin, CD34, and gliofibrilar acid protein (GFAP) were negative. Tumor cells revealed loss of INI1 expression. The EWSR1 gene rearrangement was detected by fluorescence in situ hybridization (FISH), but molecular biology failed to detect EWSR1/ETS, EWSR1/ NR4A3, EWSR1/DDIT3, EWSR1/ATF1, EWSR1-POU5F1, EWSR1/ZNF444, EWSR1-PBX1 gene fusions. The final diagnosis was soft tissue malignant myoepithelioma with rhabdoid changes and EWSR1 gene rearrangement. The differential diagnosis included soft tissue malignant rhabdoid tumor, cellular extraskeletal myxoid chondrosarcoma, proximal epithelioid sarcoma, and other soft tissue tumor with EWSR1 rearrangement. To our knowledge, this is the first case of MEC with rhabdoid features and description of fine-needle aspiration cytology. Diagn. Cytopathol. 2015;43:421-426. V C 2015 Wiley Periodicals, Inc.

Secondary EWSR1 gene abnormalities in SMARCB1‐deficient tumors with 22q11‐12 regional deletions: Potential pitfalls in interpreting EWSR1 FISH results

“…In this setting, we highly recommend evaluation of NR4A3 gene rearrangement by FISH or RT‐PCR to confirm the diagnosis of extraskeletal myxoid chondrosarcoma, as EWSR1 gene abnormalities might be secondary to large SMARCB1 deletions. Except for the above‐mentioned Ewing sarcoma study (Jahromi et al, ), there are three additional case reports describing SMARCB1‐deficient tumors with co‐existing EWSR1 rearrangements, including two myoepithelial carcinomas and one desmoplastic small round cell tumor (Machado et al, ; Soon and Petersson, ; Thway et al, ). The first myoepithelial carcinoma case was reported to have an unbalanced EWSR1 translocation (one normal EWSR1 pair signal and an isolated green telomeric signal), (Thway et al, ) similar to our Case no.…”

“…4, which suggests the loss of derivative chromosome 22 that contained the critical 5' end of EWSR1 gene. The second myoepithelial carcinoma case showed rhabdoid cells and myxoid background, and despite the EWSR1 rearrangement reported by FISH there was no identified fusion partner (Machado et al, ). The third case was a cytokeratin and desmin‐negative desmoplastic small round cell tumor which by RT‐PCR showed an EWSR1‐WT1 transcript, but by FISH had one pair of EWSR1 break‐apart signals, indicating monosomy 22 or allelic deletion (Soon and Petersson, ).…”

Application of ancillary studies in soft tissue cytology using a pattern‐based approach

“…Myoepithelial tumors of soft tissue (myoepithelioma, myoepithelial carcinoma) are characterized by architectural and cytologic heterogeneity . Smears show a spectrum of epithelioid, plasmacytoid, spindled, and occasionally rhabdoid cells associated with fibrous or myxoid stroma . Myoepithelial carcinoma is defined by cytologic atypia .…”

“…41 Smears show a spectrum of epithelioid, plasmacytoid, spindled, and occasionally rhabdoid cells associated with fibrous or myxoid stroma. [42][43][44] Myoepithelial carcinoma is defined by cytologic atypia. 41 Tumors show variable staining for keratin, EMA, S100, SOX10, GFAP, and p63.…”

Pleomorphic rhabdomyosarcoma of the submandibular gland: Diagnosis on a cytology sample

“…Furthermore, because of morphological diversity among different parts of a tumour, FNAC from PRMS are even more complicated to correctly diagnose due to the smaller tumour sample compared to a biopsy specimen. In the case of rhabdomyoblastic differentiation, the cytological differential diagnosis is difficult, particularly as rhabdomyoblasts in some small round cell tumours resemble blasts, especially lymphoblasts . Our initial differential diagnosis based on the monomorphic pattern included blastoid‐like lymphoma and small blue round cell tumours.…”