Defining fast-growing melanomas: reappraisal of epidemiological, clinical, and histological features.

The growth rate (GR) of melanomas is not uniform. A fast-growing subtype has been identified and seems to have a role in the stabilization of the mortality rates because of melanoma. To examine features associated with fast-growing melanomas (FGMs) and to determine the relationship between the GR and well-recognized prognostic factors of melanoma, a series of 386 new invasive cutaneous melanomas seen during 2004-2009 were retrieved from our database. The GR was calculated according to earlier published studies. FGMs were defined as those whose GR was greater than 0.49 mm per month. Differences in clinical, epidemiological, and pathological features were evaluated. Correlations between the GR, tumor thickness, and mitotic rate were also analyzed. FGMs were significantly more prevalent among patients aged over 65 years and with a higher rate of past personal history of nonmelanoma skin cancer. This subtype was over-represented among melanomas located on both nonexposed and usually exposed skin and was less related to earlier sunburns. Patients with FGMs presented with more aggressive pathological features and had more advanced disease with sentinel node analysis affected in up to 35% of cases. There was a strong positive correlation between the GR and tumor thickness (r=0.762), and mitotic rate (r=0.542). This study was limited by being retrospective in nature. FGMs are a highly aggressive subtype of melanomas that seem to develop after at least two routes, one related to chronic sun exposure and another unrelated to the sun. Older patients have a higher predisposition to develop this kind of tumor. This variant warrants specific strategies to improve primary and secondary prevention.