EWSR1-ATF1 Fusion in a Myoepithelial Carcinoma of Soft Tissue With Small Round Cell Morphology: A Potential Diagnostic Pitfall

Abstract

Myoepithelial tumors of soft tissue are rare mesenchymal neoplasms that overlap with their salivary gland and skin counterparts at both the histopathologic and molecular levels. EWSR1 gene rearrangements with various fusion partners represent a common genetic event in myoepithelial tumors of soft tissue, whether benign or malignant, and may prove useful as a diagnostic tool in difficult cases. However, the number of diagnostic entities with EWSR1 gene rearrangements has grown considerably in recent years, and there is significant morphologic and immunophenotypic overlap amongst this group, underscoring the importance of fusion testing to detect fusion partners that are characteristic of discrete diagnostic entities. Herein, we report a malignant myoepithelial tumor of soft tissue/myoepithelial carcinoma with an undifferentiated round cell morphology arising in a pediatric patient with a EWSR1-ATF1 gene fusion.

Primary lung hyalinizing clear cell carcinoma: a diagnostic challenge in biopsy

“…The EWSR1 gene rearrangement has been documented in both these types of cancers. Leckey Jr. et al [ 16 ] reported a case of myoepithelial carcinoma of soft tissue with small round cell morphology having EWSR1-ATF1 gene fusion, but Skálová et al [ 17 ] found that clear cell myoepithelial carcinoma with EWSR1 gene rearrangement frequently involved PLAG1 gene fusions but no EWSR1 fusion transcripts, while EWSR1-ATF1 gene fusion has been observed in most cases of HCCC [ 18 ]. We used FISH detection on the EWSR1-ATF1 chimeric gene.…”

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“…These findings must strengthen or complement a conventional pathological diagnosis based on histological and immunohistochemical findings, anticipating further accumulation of the genetic and molecular findings. Concerning benign to malignant myoepitheliomas, EWSR1and FUS-related fusion genes with various partner genes have been detected [30][31][32][33]. In 2020, Suurmeijer, et al [17] reported that fusion genes involving EWSR1 and FUS were detected in 49 of 66 cases of benign to malignant myoepitheliomas.…”