High-mitotic-rate primary cutaneous melanomas more often occur on the head and neck and in men, older patients, and those with a history of solar keratosis, according to a study published online in JAMA Dermatology.

Sarah Shen, M.B.B.S., from the Alfred Hospital in Melbourne, Australia, and colleagues conducted a cross-sectional study of patients from a multidisciplinary melanoma clinic to examine the clinicopathological associations of high-mitotic-rate melanoma. Data were included for 1,441 patients with 1,500 primary invasive melanomas.

The researchers found that high-mitotic-rate melanomas were more likely to occur in men, patients aged 70 years or older, and those with a history of solar keratosis (odds ratios [ORs], 1.5, 2.1, and 1.3, respectively). These melanomas were more likely to occur on the head and neck (OR, 1.4) and more often presented as amelanotic and rapidly growing (≥2 mm/month) lesions (ORs, 1.9 and 12.5, respectively).

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A higher mitotic rate was associated with nodular melanoma subtype (versus superficial spreading), greater tumor thickness (versus ≤1 mm), and ulceration. In the overall multivariate analysis, these histopathological features remained significant, together with amelanosis and rate of growth.

“High-mitotic-rate primary cutaneous melanoma is associated with aggressive histologic features and atypical clinical presentation,” the authors write.

  1. Shen, Sarah, MBBS, BMedSci, et al. “Characteristics and Associations of High-Mitotic-Rate Melanoma.” JAMA Dermatology. doi:10.1001/jamadermatol.2014.635. August 20, 2014.