28154 Endocrine mucin-producing sweat gland carcinoma in a patient with metastatic melanoma

Abstract

A 55-year-old male with metastatic melanoma recently off immunotherapy presented with a 1-year history of an asymptomatic, slow growing mass on his right eyelid. Examination revealed a 3-mm well-circumscribed flesh-colored papule on the right upper eyelid margin. Excision performed by oculoplastics showed a multinodular superficial cystic and deep solid dermal neoplasm. The cystic component was comprised of an epithelial lining two layers thick. The deep solid component had foci of papillary change. Lesional cells had nuclear contours with small nuceloli and sparse pale granular eosinophilic cytoplasm. Scattered mitoses were present and high-grade atypia was absent. The tumor was positive for chromogranin A, CK7, EMA, BerEp4, synaptophysin (patchy), ER, and PR. MelanA, CK20, and CD56 were negative. P63 highlighted myoepithelial cells around the tumor. Based on the histopathologic and immunohistochemical features, endocrine mucin-producing sweat gland carcinoma (EMPSGC) was diagnosed. EMPSGC is an uncommon low-grade carcinoma with histopathologic and immunohistochemical features of solid, papillary breast carcinoma. Diagnosis can be difficult given its rarity and broad clinical differential diagnosis. The key immunohistochemical feature is neuroendocrine expression; tumors also often co-express estrogen and progesterone receptors. Elaboration of a myoepithelial layer surrounding the tumor is prudent to evaluate for invasive tumor. Although EMPSGC is a low-grade carcinoma with no reported cases of metastases, complete surgical excision is recommended given local recurrence and concern for progression to invasive mucinous carcinoma. Our patient’s tumor was completely excised via Mohs micrographic surgery with closure by oculoplastics. To our knowledge, there is no known association between EMPSGC and melanoma.