Squamoid eccrine ductal carcinoma: A diagnostic challenge

Squamoid eccrine ductal carcinoma (SEDC) is a rare primary cutaneous tumor that exhibits both squamous and adnexal ductal differentiation. We report a case of SEDC presenting as multiple nodules on the scalp of a 58-year-old man. Histopathological examination of the excised lesion showed a tumor in the dermis composed of duct-like structures that represented the eccrine component and squamoid cells in nests and in an infiltrating pattern. Immunohistochemical (IHC) positivity for cytokeratin 5/6, epithelial membrane antigen (EMA), and p63 confirmed the squamoid, ductal, and primary cutaneous nature, respectively, and differentiated it from eccrine poroma, microcystic adnexal carcinoma, and porocarcinoma with squamous differentiation. With a demonstrated invasive potential, recurrent nature, and ambiguous metastatic potential, Mohs micrographic surgery, an established and successful, yet tissue-sparing surgical modality with lower recurrence rate, is the recommended treatment of choice and a close follow-up of these patients is suggested for further experiences of this tumor.