The PubMed and Ichushi databases were searched to identify cases of spontaneous regression of cancer that were featured in original papers and abstracts presented at conferences and these cases were examined. First,6 3 cases of spontaneous regression reported from Japan in 2011 were examined in detail. The most common types of cancer were lymphoma,hepatic carcinoma,and pulmonary cancer. The incidence of spontaneous regression was estimated at 1 per 12,000 patients with cancer and was calculated on the basis of the estimated number of patients who were newly diagnosed as having cancer during 1 year in Japan. Next, 83, 40,and 37 cases of spontaneous regression of hepatic carcinoma,pulmonary cancer,and lung metastases from primary malignant tumors,respectively,reported worldwide between 2006 and 2011, were analyzed. The cause of spontaneous regression in all 3 pathologies often involved an immunological mechanism. Other common factors that contributed to spontaneous regression were impaired tumor blood flow in patients with hepatic carcinoma,paraneoplastic syndrome in those with pulmonary cancer,and removal of the primary tumor in patients with lung metastasis.