Clinicopathological comparisons of index and second primary melanomas in paediatric and adult populations

The high incidence of cutaneous melanoma globally has sparked interest in the features associated with second primary melanomas (SPMs).

To identify differences and similarities between index and second primary melanomas while comparing the absolute and relative risk of subsequent melanoma development in paediatric and adult patients.

A retrospective analysis of patients diagnosed with invasive malignant melanoma from 1973 to 2008 inclusive was completed with data obtained from the Surveillance, Epidemiology and End Results (SEER) database.

In total, 208,289 patients were diagnosed with invasive melanoma in the SEER database from 1973 to 2008, with subsequent primary melanomas diagnosed in 6888 (3.3%). The incidence of SPMs increased with increasing age of diagnosis of the patient's first melanoma. However, the relative risk of developing a subsequent melanoma was nearly double for patients diagnosed with their first melanoma at the age of 19 years and younger compared with patients greater than the age of 19 years. Compared with a patient's initial invasive melanoma, 44% of the subjects had a different melanoma subtype with their subsequent melanoma. SPMs were located in a different anatomical site from the index malignancy in 55% of patients. Nodular melanomas were more common as index melanomas compared with SPMs.

Although invasive cutaneous melanoma is primarily a malignancy of adulthood, the heightened relative risk of SPMs in the paediatric population calls for careful long-term scrutiny in this latter population following an index melanoma diagnosis.