Scalp melanoma: Distinctive high risk clinical and histological features

Scalp melanoma has a worse prognosis than melanoma elsewhere, though the reasons for this are poorly understood. Current literature describing the clinicopathological associations of scalp melanoma is sparse. This study aims to compare clinical and histological features of scalp melanoma with other cutaneous head and neck melanomas (CHNM).

A cross-sectional study was performed of all primary CHNM cases seen by the Victorian Melanoma Service between 1994 and 2014, using prospectively recorded clinical data. Invasive and in situ melanomas were compared separately.

Invasive scalp melanoma was associated with male sex (OR, 2.7; 95% CI, 1.9-3.9), increasing age (OR, 1.02 per year increase in age; 95% CI, 1.01-1.03), being first noticed by a person other than self, spouse/relative or doctor (OR, 2.9; 95% CI, 1.5-5.7), amelanosis (OR, 1.6; 95% CI, 1.1-2.3), and increased growth rate (OR, 1.14 per 1 mm/month growth rate increase; 95% CI, 1.04-1.26). Compared with other CHNM, scalp melanoma had greater median Breslow thickness (2.8  vs 1.2 mm) and was independently associated with satellite metastases (OR, 4.7; 95% CI, 1.9-11.5) and nodular subtype (OR, 1.8; 95% CI, 1.1-3.1). In situ scalp melanoma was associated with male sex, increasing age and solar keratoses.

Scalp melanoma tends to occur in older men, is often rapidly growing and amelanotic, and is associated with high risk histological features. As it is likely to be overlooked, increased recognition of the atypical presentations of scalp melanoma is required.