Spiradenocarcinoma of the scalp.

Spiradenocarcinoma is an exceedingly rare malignant neoplasm with ductal differentiation. Many consider it to be an eccrine neoplasm, and others favor apocrine differentiation. In nearly all cases, spiradenocarcinoma is associated with a benign spiradenoma, with most lesions appearing on the trunk and extremities. We describe a patient who presented with a long-standing and previously asymptomatic scalp nodule that became tender and enlarged. After diagnosis of spiradenocarcinoma, the patient was referred for lymphoscintigraphy, sentinal lymph node biopsy, and Mohs micrographic surgery.