Clinical features of superficial spreading melanomas with zones of regression.
To assess the significance of spontaneous regression in superficial spreading melanoma (SSM), 36 patients with clinical signs of regression in their primary tumor were compared to 200 patients with regular SSMs (controls). SSMs with regression were found to have the following, distinctive clinical features, which were significantly different from controls (P less than 0.05): (1) male predominance (69%), (2) preferential localization on the trunk (80.6%), (3) lower tumor thickness (Breslow), (4) clustering in Clark levels II and III, and (5) a larger surface area. The incidence of metastases was lower in patients with regressing SSMs (13.9%) compared to controls (20.5%) although the time until relapse was slightly shorter (20.6 months versus 28.1 months for controls). These prognostic parameters were not significantly different. However, of the patients who died, 2 of 4 with zones of regression had thin melanomas (less than or equal to 1.5 mm), compared to only 1 of 27 without regression zones (P less than 0.05). SSMs with regression therefore have unique clinical features, which may be related to their pathogenesis, and they may have some prognostic significance.