[Complete regression of melanocytic nevi: correlation between clinical, dermoscopic, and histopathologic findings in...

The complete regression of melanocytic tumors, confirmed by histology, has rarely been reported in the literature. It is very difficult to determine the malignant or benign nature of a regressed tumor, and on occasions, the only indication of malignancy is the subsequent development of metastasis.

We performed a descriptive study of melanocytic nevi that had undergone complete, histologically confirmed regression prior to excision in the dermatology department of our hospital over a period of 3 years. We included only lesions in which dermoscopy performed prior to regression showed features that suggested benignity. We assessed various clinical, dermoscopic, histologic, and immunohistochemical features.

The mean time to complete regression was 6.4 months. The main dermoscopic patterns observed were reticular and mixed reticular/globular. Unlike what is generally seen in melanomas, the main histologic finding was the presence of fine or lamellar fibrosis. In all cases, there was a predominance of CD8+ T cells.

The clinical, dermoscopic, and histologic features of the melanocytic nevi studied suggest the existence of a highly characteristic form of tumor regression characterized by very rapid regression and the involvement of a cytotoxic mechanism.