A study of histopathological features of medullary carcinoma of the thyroid: cases from a single institute in India.

BACKGROUND The microscopic features of medullary carcinoma have been described in world literature, together with its behavior and molecular biology. However, no large study has been reported from India. AIMS This study aims to analyse the clinical, and especially the pathological features of medullary carcinoma of the thyroid, and the surrounding thyroid. MATERIALS AND METHODS In this study a total of 234 cases of medullary thyroid carcinoma (MTC) were gathered over a period of 3 decades. The clinical presentation, the microscopic features and the clinical outcome were analyzed. RESULTS MTC was found to be twice as common in men as in women and for some reason it occurred 10 years earlier in women. The histology revealed certain interesting features like the presence of apoptosis in over half of the tumors, in addition to the other common and not so common histological findings (encapsulated variant, small cell variants, follicular pattern, rosettes, oncocytic change, osteosarcoma-like pattern, and cribriform pattern). The adjacent thyroid in about 19% of the cases showed optically clear nuclei in the follicles that were close to the tumor cells. These features were similar to those seen in papillary thyroid carcinoma. CONCLUSIONS The thyroid adjacent to MTC showed nuclear changes, which are also found in papillary carcinoma of the thyroid. The occasional concurrent occurrence of these two tumors and the involvement of the RET gene in both medullary and papillary carcinomas, makes this observation worth discussing and studying further.