Microcystic adnexal carcinoma (MAC) of the scalp with extensive pilar differentiation.

BACKGROUND

Microcystic adnexal carcinoma (MAC), or sclerosing sweat duct tumor, is an uncommon, locally aggressive tumor. It typically involves the upper lip or face of middle-aged adults and rarely involves the scalp. It is characterized histologically by both pilar and eccrine differentiation and is associated with frequent perineural invasion. MAC is frequently misdiagnosed because of its bland and asymptomatic clinical presentation. In addition, its defining histologic features may be missed with a superficial biopsy.

OBJECTIVE

To describe a case of MAC in the scalp treated with Mohs surgery. We describe a case with extensive pilar differentiation and clear cell changes. In addition, the clinical and histologic characteristics of this rare neoplasm are reviewed.

METHODS

Mohs micrographic surgery (MMS) was performed on this neoplasm.

RESULTS

The tumor was successfully excised in one surgery (five stages) and is without evidence of recurrence at 18 months.

CONCLUSION

We present a case of MAC of the scalp in a 64-year-old white man treated successfully with MMS.