Spontaneous regression of malignant melanoma - is it based on the interplay between host immune system and melanoma antigens?

Malignant melanoma (MM) is the most aggressive and uneasily treatable form of skin cancer. Up to 90% of deaths because of skin tumours are estimated to be caused by this malignancy. Spontaneous regression is described as a partial or complete disappearance of cancer. It can be defined if the clinical and histological diagnosis of malignancy is verified and any therapeutic intervention potentially inducing mechanisms leading to regression has not been applied. Regression occurs more frequently in melanoma than in other types of tumours; it is reported to be six times higher than in other malignancies. Up to 50% of primary MM is reported to undergo spontaneous regression. However, spontaneous regression of the metastatic form of tumour is a rare phenomenon observed in only 0.23% of cases. The most frequently mentioned factors leading to spontaneous regression of MM are operative trauma, infection, vaccination (BCG and rabies vaccines) and immunological factors. Other well-documented circumstances associated with regression of metastatic MM include blood transfusion and various endocrine factors.