High-mitotic rate melanoma linked to patient, tumor characteristics

Issue: December 10, 2014

Melanomas with higher mitotic rates occurred more frequently in men and in individuals aged older than 70 years, according to results of a cross-sectional study.

These melanomas often presented with aggressive histologic features, results showed.

Sarah Shen, MBBS, BMedSci, of Alfred Hospital in Victoria, Australia, and colleagues evaluated data from 1,441 patients diagnosed with 1,500 primary invasive melanomas between 2006 and 2011. Researchers classified each patient’s mitotic rate as 0, ˂1, 1 to ˂2, 2, 3-4, 5-9, and ≥10 mitoses per mm².

Men (OR=1.5; 95% CI, 1.3-1.8) and those aged older than 70 years (OR=2.1; 95% CI, 1.7-2.8) more frequently presented with high-mitotic rate melanomas. Melanomas with higher mitotic rates also were more common in patients who had a history of solar keratosis (OR=1.3; 95% CI, 1.1-1.6).

However, patients were more likely to have a lower mitotic rate if they had a history of blistering sunburns (P=.02) and a clinically significant family history of melanoma (P˂.001).

The lesions of high-mitotic rate melanomas were more likely to occur on the head and neck (OR=1.4; 95% CI, 1-1.9), and they also were more likely to be amelanotic (OR=1.9; 95% CI, 1.4-2.5) and rapidly growing with ≥2 mm of growth per month (OR=12.5; 95% CI, 8.4-18.5).

A high mitotic rate occurred more frequently with nodular melanoma subtype vs. superficial spreading (OR=2.25; 95% CI, 1.8-3.4), and it occurred more frequently in melanomas with tumor thickness ˃1 mm to 4 mm (OR=4.5; 95% CI, 3.2-6.1) or ˃4 mm (OR=12.6; 95% CI, 7.5-21.1) compared with thickness ≤1 mm. Ulceration also was common in these melanomas (OR=2; 95% CI, 1.5-2.7).

Nodular tumor type (P˂.001), ulceration (P˂.001), ˃4 mm tumor thickness (P˂.001), rate of growth (P=.01) and amelanosis (P=.03) remained significantly associated with mitotic rate in a multivariate analysis.

Samuel J. Balin

“The results from this single-center study merit replication elsewhere to confirm generalizability and to further explore the potential implications for detection and treatment of at-risk patients, who in this study were found to have a distinct phenotypic and historical profile,” Shen and colleagues concluded. “Such atypical clinical features may pose a challenge to timely detection; thus, a high index of suspicion is warranted when the patient reports a history of morphologic change and rapid growth.”

These patient and tumor characteristics may help physicians determine which lesions to biopsy, Samuel J. Balin, MD, PhD, of David Geffen School of Medicine at UCLA, and Raymond L. Barnhill, MD, MSc, of UCLA Medical Center, wrote in an accompanying editorial.

“The decision to biopsy is influenced by many factors, including history, symptoms, location, and most of all appearance of the lesion. Shen et al provide clinicians with more data and ultimately another tool to factor into their clinical decision-making process,” Balin and Barnhill wrote. “By understanding the clinical characteristics of more rapidly growing tumors, clinicians can better guide their own screening and treatment decisions and better counsel patients, from diagnosis through treatment, and ultimately to prognosis.”

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Disclosure: The researchers report no relevant financial disclosures.