Prognostic Factors of Thin Cutaneous Melanoma: An Analysis of the Central Malignant Melanoma Registry of the German Dermatological Society

Purpose The increasing number of thin cutaneous melanomas (CM) with tumor thickness up to 1 mm demands a detailed analysis of prognostic factors for the classification and grading of these tumors. The aim of the present study was to identify prognostic factors in thin CM. Patients and Methods A series of 12,728 patients with thin incident primary invasive CM and follow-up data recorded between 1976 and 2000 by the German-based Central Malignant Melanoma Registry was analyzed using the multivariate Cox proportional hazard model to evaluate prognostic factors, and classification and regression trees analysis (CART) to define prognostic groups. Results Multivariate analysis found tumor thickness, sex, age, body site, and histopathologic subtype to be significant prognostic factors of thin CM. Ulceration and regression did not affect prognosis significantly. Prognostic classification based on the results of CART analysis resulted in three groups defined by tumor thickness, age, and sex. Ten-year survival rates of these groups varied between 91.8% and 98.1%, with improved classification as compared with subgroups by tumor thickness alone. Conclusion Classification by tumor thickness identified prognostic subgroups with highest significance in thin CM, and the classification was improved by the introduction of age and sex. However, neither ulceration nor the level of invasion included in the new American Joint Committee on Cancer TNM system classification, revealed statistical significance as prognostic factors in thin CM.