Pattern of second primary malignancies in thyroid cancer patients.

Many factors, including relatively young age of thyroid cancer diagnoses and improved survival, have led to increased concerns about the occurrence of second primary malignancies. This paper describes the pattern of occurrence of second primary malignancies in patients who were treated for malignant thyroid neoplasms in an Indian hospital. There were 21 affected patients of the approximately 4500 seen over 25 years. Most of the second primary cancers are solid tumors, and when nonthyroid cancers are the second tumors, ductal carcinoma of the female breast is the most common. Most of these tumors have very short detection intervals (including synchronous occurrences), suggesting that therapy with internal radiation was not contributory to the tumor development. When thyroid malignancies were the second primary cancers, they usually follow radiotherapy to the head and neck region for treatment of the first primary tumor and tend to be of aggressive histologic types than the common well differentiated thyroid carcinomas.