Nevus-associated melanomas, or melanomas that are associated with a mole, are less likely to have an adverse histopathology (microscopic study of tissue) than de novo melanomas, which arise from clinically normal skin without an associated mole.
According to the study “De Novo vs Nevus-Associated Melanomas: Differences in Associations With Prognostic Indicators and Survival,” published in the Journal of the National Cancer Institute, the overall survival of patients with nevus-associated melanomas is also better than that of patients with de novo melanomas.
“These findings suggest there are potentially important differences in the biology of nevus-associated and de novo melanomas,” wrote study author Dr. Rachel M. Cymerman, resident physician at The Ronald O. Perelman department of dermatology at New York University School of Medicine, according to a news release.
Cymerman and colleagues analyzed data from two cohorts of melanoma patients treated at New York University, the first between 1972 and 1982, and the second between 2002 and 2009. Both cohorts included more than 1,000 patients, with more than 80 percent in the first cohort and almost 70 percent in the second cohort diagnosed with de novo melanomas.
The researchers found that for both cohorts, patients with de novo melanomas tended to have a tumor thickness bigger than 1 mm, ulceration (where the tumor spreads through the overlying epidermis), nodular subtype, and stage 2 disease or higher.
These patients also tended to be older and have a shorter overall survival compared to patients with nevus-associated melanomas.
They concluded that a de novo classification of a melanoma is independently associated with a poorer prognosis and that it may be useful to use the nevus-associated vs. de novo classification when analyzing melanoma risk factors, tumor biology, and response to therapy.
Melanomas arise de novo, or without a mole, in 70 to 80 percent of cases, and are associated with moles in only 20 to 30 percent. This study points to the importance of classifying melanomas accordingly so that their biology and response to treatment can be better predicted.