Why do melanomas ulcerate?

Ulceration is an indicator of unfavourable prognosis in malignant melanoma (MM). But why do melanomas ulcerate?. Possible causes of ulceration were investigated in a group of 69 ulcerated and 69 non-ulcerated malignant melanomas. A significant correlation (P less than 0.001) between ulceration and mitotic index was found. In a group of 69 ulcerated malignant melanomas, 49 had over 7, 15 had 4-6, and only 5 had 0-3 mitotic figures per 10 high-power fields. Among 69 non-ulcerated melanomas, 28 had more than 7, 24 had 4-6, and 17 had 0-3 mitotic figures per 10 high-power fields. This study supports the hypothesis that ulceration of melanomas is usually the result of the destruction of the epidermis by the proliferating neoplastic cells or modification of blood supply due to the expansile activity of the tumor. The relationship between ulceration and mitotic activity helps clarify the prognostic significance of ulceration.