An Elderly Patient With Prostate Cancer and Colon Cancer 10 Years After a Diagnosis of Medullary Thyroid Carcinoma

Medullary thyroid carcinomas (MTC) are rare tumors that account for approximately 5-10% of all thyroid malignancy in the West. The reported incidence of MTC is less than 5% in Korea. Its prognosis is relatively good with a 15-year survival rate of 64-84%. The incidence of thyroid cancer has been increasing rapidly worldwide and the overall survival of patients with thyroid cancer is excellent. The occurrence of second primary malignancy (SPM) among survivors of thyroid cancer is a concern, together with life expectancy. Recent studies reported a 6-45% increase in the risk of developing SPM after the diagnosis thyroid cancer. We reported a patient with prostate and colon cancer that were diagnosed 10 years after the diagnosis of medullary thyroid carcinoma.