Microcystic adnexal carcinoma induced by multiple radiation therapy

We present an 84-year-old Caucasian man (Fitzpatrick classification: skin t ype II) with microcystic adnexal carcinoma (MAC) on his left cheek and a 15 -year history of recurrent squamous cell carcinoma (SCC) of the head, treat ed with numerous surgical interventions and multiple palliative 60-Gy radia tion therapy. In 1996, the patient developed a nontender, indurated, irregularly marked, erythematous lesion on his left cheek (1.5 x 1 cm). Furthermore, the patien t suffered from radiodermatitis due to previous radiotherapy (Fig. 1). Punc h biopsy and a subsequent wedge excision showed features of both SCC and ec crine carcinoma. Histopathologic and immunohistochemical tests of the tumor revealed a diagnosis of MAC. The patient underwent Mohs' micrographically controlled surgery to obtain tumor-free peripheral soft tissue margins. The re was no evidence of any lymphatic invasion or distant metastasis in the p hysical and laboratory examination. So far, the patient has not developed a ny recurrences. Following excision, the biopsy specimen (4 x 2.6 x 1 cm) was fixed in Dubos q-Brazil and routinely processed for staining with hematoxylin and eosin. T he neoplasm extended into the subcutaneous tissue with rare connection to t he overlying epidermis (Fig. 2). Follicular cysts with amorphous eosinophil ic keratin and comma-like tails of aggregates of epithelial cells were a pr ominent feature (Fig. 3). Perineural invasion was evident, but there were o nly a very few mitotic figures. Immunohistochemistry on paraffin-embedded t issue blocks was performed, showing strong labeling on dilated ducts for ca rcinoembryonic antigen (CEA), epithelial membrane antigen (EMA) in the lumi na of tumor cells, and positive staining for anticytokeratin KL1 (55-57 kDa ) and S-100 protein. The latter was negative in ductal structures, but stai ned dendritic cells.