Pathologic and clinical features influencing outcome of thin cutaneous melanoma: Correlation with newly proposed staging system

The incidence of malignant melanoma is increasing. Because of increased awa reness, early recognition of malignant melanoma has become more common. In 1997, a new staging system for cutaneous melanoma was proposed, with reclas sification of thin melanoma < 1 mm, with and without ulceration. This repor t evaluates the pathologic and clinical features of thin melanomas influenc ing recurrence and survival from a tertiary cancer center in an attempt to correlate findings with the proposed staging system. A review of the Roswel l Park Cancer Institute tumor registry identified 352 patients with thin cu taneous 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, respecti vely. Disease-free survival was 94 and 93 per cent at 5 and 10 years, respe ctively. Local recurrence occurred in 3 per cent of patients, regional recu rrence 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 p resence 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 wa s 40 and 94 per cent, respectively (P < 0.0001). We conclude that thin cuta neous melanoma carries an excellent prognosis with appropriate treatment. O ur findings support inclusion of ulceration in a new staging system. Lesion s 0.76 to 0.99 mm and Clark level III and IV may warrant close observation as a separate subgroup.