A functioning pleomorphic carcinoma of the thyroid.

A metastasizing functioning pleomorphic carcinoma of the thyroid displayed a morphologic piture ranging from follicular to sarcomatous and carcinoid-like patterns. Spindle-cell elements were believed to be the result of metaplasia of the follicular epithelium. Development of carcinoid-like lesions in the secondary deposits of tumour supported the contention that so-called parafollicular or c-cells may be a phenomenon of metaplasia and not a histologic entity. The tumour was associated with a chromophobe adenoma of the pituitary and a benign schwannoma of the stomach. Clinically the patient did not show any other endocrinologic abnormalities and lived for 4 years from the time of diagnosis of the thyroid tumour.