Medullary carcinoma of the thyroid with ectopic ACTH syndrome.

An autopsied patient with medullary carcinoma of the thyroid and ectopic ACTH syndrome is reported. A microadenoma of pancreatic islet coexisted in this case, which is assumed to be of D cell origin. Immunohistochemical study revealed decreased number of pituitary ACTH cells. Some of them showed Crooke's degeneration. Hormone assay study of tumor tissue and plasma disclosed abnormal ACTH, beta-MSH as well as calcitonin. Somatostatin and Substance P were also demonstrated in tissue. Histologically the tumor showed solid alveolar pattern with a minor part consisting of small cell variant and this histologic variation is discussed.