The treatment options in renal cancer are few and the response rates are low. It is also a cancer form that has a diverse biology-the vast majority of cases progress rapidly but in a small fraction of patients the progression occurs slowly and in rare cases spontaneous regression are known to occur [1]. These have been reported in virtually all types of human cancer, although the greatest numbers of cases are reported in neuroblastoma, renal cell carcinoma, melanoma and lymphomas/leukemias. Spontaneous regression of cancer is an interesting phenomenon and elucidating the mechanisms by which it occurs offers the hope that more effective methods of treating and preventing cancer could be developed.

In renal cell carcinomas spontaneous regression predominate in males by a ratio of 3: 1. In over 90% of cases, pulmonary metastases are the site of regression. Regression of other sites such as skin, liver, intestine, bone and nodal areas have also been reported [2]. Most frequently spontaneous regression occurs after nephrectomy but the phenomenon has been reported in the absence of surgery or after vascular embolisation, radiofrequency ablation and radiotherapy [1].