Spontaneous regression of cancer

introduction Spontaneous regression of cancer is one of the most fascinating phenomena observed in medicine. It is generally regarded as inexplicable, although there are now some laboratory studies of regressed or regressing tumours, as well as new theoretical possibilities about mechanisms. In this review, the historical background, clinical features and possible mechanisms are discussed. The clinical aspects of the malignancies most often reported to undergo spontaneous regression, namely renal cell carcinoma, neuroblastoma, carcinoma of the breast, malignant melanoma and leukaemias/lymphomas, are reviewed. The prevalent view regarding the mechanism for spontaneous regression is the involvement of immunological factors in the host. Other mechanisms include hormonal changes, tumour necrosis, trauma and changes in blood supply. Recent. reports suggest other mechanisms such as apoptosis and differentiation to a benign tumour. Decreased telomerase activity has been reported in neuroblastomas that regress, and hypomethylation of DNA in