Prognosis of naevoid melanomas

Introduction: There appear to be several variants of naevoid melanoma suspected as having different outcomes, but follow-up studies have been few. We aimed to assess the prognosis of naevoid melanomas in a multi-centre study.

Material and methods: From histopathology records we ascertained patients in the UK, Australia and Italy diagnosed with maturing naevoid melanoma (n = 65; 14; 7 respectively) and nodular/papillomatous naevoid melanoma (12; 6; 0), and patients with superficial spreading melanoma (SSM) from UK (73) and Australia (26). Melanoma deaths in UK patients were obtained from NHS Digital; in Australia, via the National Death Index and cancer registry; and in Italy, through clinical records. For maturing naevoid vs. SSM, we used Cox-proportional hazard regression models to compare survival adjusted for age, sex, tumour thickness, and ulceration, and additionally Fine-Gray regression analysis, to calculate sub-hazard ratios (SHR) in the UK cohort, accounting for competing causes of death.

Results: Among UK patients, there was a non-significantly lower risk of melanoma death in maturing naevoid vs SSM, including after accounting for competing causes of death (SHR 0.40, 95% confidence interval (CI) 0.12-1.31), while among nodular/papillomatous naevoid melanoma patients, there were no melanoma deaths on follow-up. Two melanoma deaths occurred in Australian SSM patients, and none in maturing or nodular/papillomatous naevoid melanoma patients, after 5 years' minimum follow-up. None of the 7 Italian patients with maturing naevoid melanoma died of melanoma after nearly 12 years' average follow-up.

Conclusions: There was no significant difference in risk of death from melanomas with naevoid features, and SSM. Nodular/ papillomatous naevoid melanoma patients did not carry higher risk of death than SSM patients though the very few cases of the papillomatous naevoid variant limited our assessment.