Abstract

Squamoid eccrine ductal carcinoma (SEDC) is a very rare skin tumor which is often misdiagnosed as squamous cell carcinoma on biopsy specimens. Due to rarity of the tumor and difficulties in diagnoses, molecular characteristics of these lesions are not well understood. Here, we report a case of SEDC that we studied with next-generation RNA sequencing fusion panel to identify gene rearrangements. Male patient, 42 years old, with no significant past medical history, presented with 1 cm evolving nodular mass on his scalp that sloughed off every time he got a haircut. An incisional biopsy was performed, and a diagnosis of adenoid squamous cell carcinoma was made. On excision, an infiltrative neoplasm with striking biphasic dermal and subcutaneous components was seen. The superficial portion showed unequivocal squamous differentiation reminiscent of squamous cell carcinoma, meanwhile deep portion showed nested multinodular growth pattern of numerous squamoid cells with ductal differentiation. Nuclear atypia was severe and perineural invasion was present. Ductal differentiation was confirmed by immunohistochemistry with EMA and CD117. Subsequent molecular analysis was performed using targeted RNA sequencing panel FUSION-SEQer. A total of 106 genes known to be recurrently involved in cancer associated rearrangements were included in the panel design. Our analysis revealed a YAP1-NUTM1 fusion which was confirmed by reverse transcription polymerase chain reaction. This gene rearrangement is typically enriched in porocarcinoma and poromas among other eccrine neoplasms. To our knowledge, there are no previous reports of this particular fusion in SEDC. Our findings support the role of YAP1 gene rearrangements as an eccrine molecular event associated with different adnexal neoplasms.

Financial Disclosure:
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