Medullary (Solid) Carcinoma of the Thyroid—a Clinicopathologic Entity*

Medullary carcinoma is characterized by a solid nonfollicular histologic pattern, the presence of amyloid in the stroma, and a high incidence of lymph node metastases. The tumor is clinically of an intermediate rather than a high grade of malignancy, despite its undifferentiated character. It is important to distinguish it from the highly malignant solid form of anaplastic carcinoma, and from papillary carcinoma, which is of a lower grade of malignancy. Twenty-one cases are reported. Fourteen patients were women and 7 were men; the ages ranged from 33 to 66 years with a median of 50 years. The regional cervical lymph nodes contained metastases at the time of initial surgery in 10 of 21 cases (48 per cent). Distant metastases occurred in 8 patients and were principally evident in the lungs, liver and bone. Amyloid, though of variable amount, was present in the stroma of all tumors of this series. The course of the disease was usually chronic; 12 patients survived six to twenty-seven years after the initial thyroid operation. Eleven patients died (6 because of neoplasm) four months to twenty-seven years after definitive surgical treatment.