Clinicopathological features of and risk factors for multiple primary melanomas

Context  The incidence of multiple primary melanomas ranges from 1.3% to 8.0% in large retrospective reviews; however, the impact of certain risk factors is not understood. Objectives  To determine the incidence of multiple primary melanomas (MPM) from a prospective, single-institution, multidisciplinary database, and to describe the clinical and pathological characteristics and risk factors specific to these patients. Design and Setting  Review of a prospectively maintained database at Memorial Sloan-Kettering Cancer Center in New York, NY. Patients  A total of 4484 patients diagnosed with a first primary melanoma between January 1, 1996, and December 31, 2002. Main Outcome Measures  Incidence of and risk factors for MPM. Results  Three hundred eighty-five patients (8.6%) had 2 or more primary melanomas, with an average of 2.3 melanomas per MPM patient. Seventy-eight percent had 2 primary melanomas. For 74% of patients, the initial melanoma was the thickest tumor. Fifty-nine percent presented with their second primary tumor within 1 year. Twenty-one percent of MPM patients had a positive family history of melanoma compared with only 12% of patients with a single primary melanoma (SPM) (P<.001). Thirty-eight percent of MPM patients had dysplastic nevi compared with 18% of SPM patients (P<.001). The estimated cumulative 5-year risk of a second primary tumor for the entire cohort was 11.4%, with almost half of that risk occurring within the first year. For patients with a positive family history or dysplastic nevi, the estimated 5-year risk of MPM was significantly higher at 19.1% and 23.7%, respectively. The most striking increase in incidence for the MPM population was seen for development of a third primary melanoma from the time of second primary melanoma, which was 15.6% at 1 year and 30.9% at 5 years. Conclusions  The incidence of MPM is increased in patients with a positive family history and/or dysplastic nevi. These patients should undergo intensive dermatologic screening and should consider genetic testing.