Medullary carcinoma of thyroid. Biologic behavior of the sporadic and familial neoplasm.

Three groups of patients with medullary thyroid carcinoma treated for cure from an institution under standardized tumor stage were compared. For sporadic cases and all cases across groups, the observed survival rates at 10 years were significantly lower than expected based on persons from the West North Central region of the US of like age and sex born in the same calendar year. They were not different for patients with multiple endocrine neoplasia (MEN), type 2a and 2b. Mean ages were significantly different among the three groups: they were 48.5 years for sporadic, 37.7 for MEN 2a, and 23.4 for MEN 2b. Tumor-free survival rate after surgical treatment of MEN 2b was 36.6% at 5 years and 27.3% at 10 years, and was significantly lower in comparison with that of sporadic cases. Medullary carcinoma in patients with MEN 2b appeared to develop at an earlier mean age, with a higher frequency of nodal metastasis and a higher rate of tumor recurrence.