Thyroid carcinoma and Cushing's syndrome. A report of two cases with a review of the common features of the "non-endocrine" tumours associated with Cushing's syndrome.

Two cases of thyroid carcinoma and Cushing's syndrome are reported. Nine other previously published cases of this association are reviewed: in one the thyroid tumour was described as medullary, in two as papillary, and in the other six as anaplastic, undifferentiated, atypical, or solid carcinoma. Both of our own cases were medullary carcinomas of the thyroid, and on reviewing the histology of five of the other cases all proved to be medullary carcinoma with identifiable amyloid in the stroma. A consideration of the temporal relationships of the development of the carcinoma and of Cushing's syndrome suggested that in the two cases with papillary carcinoma these conditions could have been unrelated, but that in eight of the nine cases with medullary carcinoma there was evidence that thyroid carcinoma was present at the time of diagnosis of Cushing's syndrome. The other main groups of the so-called ;non-endocrine' tumours associated with Cushing's syndrome are briefly reviewed, and evidence that a surprising number of these cases are related to carcinoid tumours is put forward. Medullary carcinoma of the thyroid is also probably related to this group of tumours. It is suggested that the great majority of the tumours associated with Cushing's syndrome are derived from cells of foregut origin which are endocrine in nature. In neoplasms derived from these cells the polypeptide hormone may well be imperfectly formed, and possess an amino-acid sequence in common with ACTH or other biologically active polypeptides.