Ipilimumab induces simultaneous regression of melanocytic naevi and melanoma metastases

Ipilimumab blocks cytotoxic T-lymphocyte-associated antigen (CTLA)-4, potentiating the antimelanoma T-cell host response. Ipilimumab has been shown to improve overall survival in patients with previously treated metastatic melanoma. CTLA-4 antibodies generate immune responses to the melanoma-associated antigens Melan-A, NY-ESO-1 and glycoprotein (gp)100 in metastatic melanoma. Digital epiluminescence microscopy (DELM) is a noninvasive method permitting the monitoring of the morphology of melanocytic lesions over time. A 50-year-old man with metastatic melanoma received four ipilimumab injections after failure of dacarbazine chemotherapy. Positron emission tomography revealed regression of pulmonary metastases, and simultaneously, DELM showed regression of several melanocytic naevi. On histological examination of the regressing naevi, prominent CD8+, CD4+ and CD45R0 lichenoid lymphohistiocytic infiltrates were seen, whereas nonregressing naevi were almost free of inflammatory infiltrate. Expression of melanoma-associated antigens in benign melanocytic naevi may explain the induction of naevus regression by ipilimumab. DELM could represent a valuable noninvasive method to monitor ipilimumab efficacy.