Melanoma With High Mitotic Rate Is Associated With Aggressive Histologic Features and Atypical Presentation
High mitotic rate in primary melanomas appears to be an independent predictor of poorer survival. In a single-institution study reported in JAMA Dermatology, Shen et al found that high mitotic rate primary melanoma is associated with male sex, older age, amelanosis, and several aggressive histopathologic features.
The study included data from 1,441 patients with 1,500 primary invasive melanomas seen at an Australian multidisciplinary melanoma clinic (Victorian Melanoma Service) between January 2006 and December 2011. Mitotic rate was measured as number of mitoses per mm2, with analysis according to categories of 0, < 1, 1 and < 2, 2, 3 to 4, 5 to 9, and ≥ 10.
Patient and Clinical Characteristics
On multivariate analysis, patient characteristics associated with higher mitotic rate were male sex (odds ratio [OR] = 1.4, P < .001), age ≥ 70 (OR = 1.9, P = .001), and first-degree relative with melanoma (OR = 0.7, P = .002). Clinical characteristics associated with higher rate included amelanosis (OR = 1.9, P < .001) and more rapid rate of growth (ORs = 12.5 for ≥ 2.0, 4.2 for 0.5 to < 2.0, and 2.0 for 0.2 to < 0.5 mm2 per month; P < .001), with a borderline significant relationship for location on head or neck (OR = 1.4, P = .07, vs trunk).
Histopathologic Characteristics
Histopathologic characteristics associated with higher mitotic rate on multivariate analysis included nodular subtype (OR = 2.5, P < .001, vs superficial spreading subtype), greater tumor thickness (ORs = 12.6 for > 4 and 4.5 for > 1–4 mm; P < .001), ulceration (OR = 2.0, P < .001), Clark level (ORs = 8.3, 4.6, and 3.1 for 5, 4, and 3 vs 2), and preexisting nevus (ORs = 0.3 for dysplastic and 0.7 for nondysplastic, P < .001, vs none).
The investigators concluded: “High-mitotic-rate primary cutaneous melanoma is associated with aggressive histologic features and atypical clinical presentation. It has a predilection for the head and neck region and is more likely to be seen in elderly men…who present clinically with rapidly developing disease.”
Sarah Shen, MBBS, BMedSci, of Alfred Hospital, Victoria, is the corresponding author for the JAMA Dermatology article.
The authors reported no conflicts of interest.
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