(HealthDay News) – For patients with single primary melanoma (SPM) and multiple primary melanomas (MPM), there is no significant difference in the presence or absence of mitosis, according to a study published online January 13 in Cancer.

Charlotte Hwa, of the New York University School of Medicine in New York City, and colleagues conducted a prospective study of 788 patients with melanoma to investigate the clinical and primary characteristics of SPM versus MPM.

The investigators found that 7.7% of the patients had two or more primary melanomas. The incidence of developing a second primary melanoma was 4.1% one year after initial diagnosis, and 8.7% five years after diagnosis. The incidence of MPM was higher for those patients aged 60 years and older. There was no significant difference in the absence or presence of mitosis, or other tumor characteristics, between the two groups.

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“We observed no statistically significant difference in tumor proliferation between patients with MPM and patients with SPM as measured by the mitotic rate and, thus, no difference in tumor behavior between these two groups,” the authors write. “Factors like genetics, early detection, and improved surveillance of patients with melanoma may account for the thinner tumors and enhanced prognosis in patients with MPM.”

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