Complete spontaneous regression of Merkel cell carcinoma.

Merkel cell carcinoma (MCC) is a very aggressive primary cutaneous neoplasm most often occurring on the head and neck of the elderly. Spontaneous regression of MCC was first described in 1986. A 79-year-old woman with MCC on the right cheek underwent spontaneous regression of the malignancy, documented by photographic follow-up, computed tomography, and histologic studies. A review of the literature is presented. Complete clinical and histologic regression of MCC was observed in the present case. Although the literature documents 11 similar cases, only 6 can be regarded as complete spontaneous regressions following exclusive performance of a biopsy (primary complete spontaneous regression). Primary complete spontaneous regression of MCC is infrequent, and most case reports describe this phenomenon in women with MCC on the cheek. The reasons underlying regression are unknown.