A diagnostic challenge in an atypical variant of microcystic adnexal carcinoma mimicking ulcerative basal cell carcinoma: a case report and brief literature review.

Microcystic adnexal carcinoma (MAC) is a rare adnexal tumor with eccrine and pillar differentiations with a localized and aggressive nature, often misdiagnosed as other dermatoses. The most common clinical manifestations of MAC are yellowish or skin-colored papules, nodules, and plaques. However, in some rare cases an atypical manifestation such as ulceration that resembles malignancies such as basal cell carcinoma (BCC) can also occur. Diagnosis of MAC mainly relies on the aid of histopathology. Due to potential infiltration to other structures such as in perineural invasion, wide surgical excision or Mohs micrographic surgery is the preferred surgical option. We report the case of a 75-year-old male patient with ulcerative lesion on the forehead that clinically resembled BCC in addition to typical dermoscopic findings of BCC. However, histopathology confirmed a diagnosis of MAC, prompting physicians to be more aware of this condition when encountering chronic ulcerative lesions. After wide excision and a 1-year follow-up, the patient exhibited no signs of recurrences and will continue long-term follow-up.