Analysis of histopathological factors associated with prolonged survival of 10 years or more for patients with thick melanomas (>5mm)

Aims: Although tumour thickness is the best predictor of melanoma prognosis in patients with localized cutaneous melanoma, prolonged survival occasionally occurs in patients with thick melanomas (> 5 mm). This study examined histological features which were associated with long-term survival. Methods and results: Forty-two patients with thick, vertical growth phase melanomas surviving 10 years or more after diagnosis were matched by clinical stage of disease, sex, age and anatomical site of the primary lesion with 42 patients with similar characteristics who died from their disease within 3 years of diagnosis. Fourteen histological factors were assessed in both groups, Tumours with spindle cell and Spitz-like cell populations and those with low mitotic activity were significantly more frequently observed in long-term survivors, There was also a significant excess of melanomas exhibiting desmoplasia and those lacking vascular invasion in the long-term survivors. Conclusions: These findings suggest that it may be useful to modify the current cutaneous melanoma classification on the basis of unusual cytological characteristics (as discussed at the recent 4th World Conference on Melanoma).