Pathologic and Clinical Features Influencing Outcome of Thin Cutaneous Melanoma: Correlation with Newly Proposed Staging System

Abstract

The incidence of malignant melanoma is increasing. Because of increased awareness, early recognition of malignant melanoma has become more common. In 1997, a new staging system for cutaneous melanoma was proposed, with reclassification of thin melanoma < 1 mm, with and without ulceration. This report evaluates the pathologic and clinical features of thin melanomas influencing recurrence and survival from a tertiary cancer center in an attempt to correlate findings with the proposed staging system. A review of the Roswell Park Cancer Institute tumor registry identified 352 patients with thin cutaneous melanomas (< 1.0 mm) seen during an 18-year period ending August 30, 1998. Overall survival was 93 and 87 per cent at 5 and 10 years, respectively. Disease-free survival was 94 and 93 per cent at 5 and 10 years, respectively. Local recurrence occurred in 3 per cent of patients, regional recurrence in 3 per cent, and metastatic disease in 3 per cent, for an overall recurrence of 7 per cent, with a median follow-up of 118 months. Only the presence of ulceration was a significant prognostic factor for recurrence by both univariate and multivariate analysis. Failure rates (any recurrence) by Clark levels I, II, and III/IV were 3, 5, and 10 per cent, respectively (P = 0.14). Failure rates by tumor thickness (mm), for 0.0–0.24, 0.25–0.49, 0.50–0.74, and 0.75–0.99 were 3, 4, 7, and 10 per cent, respectively (P = 0.49). Ten-year disease-free survival for ulceration versus no ulceration was 40 and 94 per cent, respectively (P < 0.0001). We conclude that thin cutaneous melanoma carries an excellent prognosis with appropriate treatment. Our findings support inclusion of ulceration in a new staging system. Lesions 0.76 to 0.99 mm and Clark level III and IV may warrant close observation as a separate subgroup.