Cytogenetics of multiple endocrine neoplasia syndromes. I. Two different, unique clonal chromosome changes in a medullary thyroid carcinoma and in a C-cell thyroid hyperplasia.

In short-term cultures of tumor tissue from a medullary thyroid carcinoma (MTC), we found a large clone of cells with a balanced translocation t(9;12)(p24;q22). A large clone with a balanced translocation t(10;16)(p11;q24) was also found in cultures from a C-cell thyroid hyperplasia. No clearcut evidence for chromosome instability was observed in the lymphocytes of the two patients. The mother of the first patient died of MTC; two relatives of the second patient had MTC and one of them had pheochromocytoma. These findings classify the two subjects as MEN 2A patients with different phenotypic expression but with the same type of chromosomal abnormality.