ACTH and calcitonin secreting medullary carcinoma of the thyroid.

SUMMARY The present report describes the case history of a woman suffering from an ectopic ACTH syndrome due to a medullary carcinoma of the thyroid. Histologic and electron microscopic studies revealed the tumorous nature of the so-called ‘macrophage-like’cell; the diagnostic significance of this cell is stressed. It appears that there is a whole spectrum of tumour cells ranging from the typical tumour cell via transitional forms to ‘macrophage-like’tumour cells. Tumour tissue was investigated for the presence of calcitonin and ACTH by immunological and biological methods. Tumour tissue sections stained specifically for calcitonin in the immunofluorescence technique; high concentrations of calcitonin could be demonstrated in tumour extracts both by radioimmunoassay and bioassay. In contrast, the presence of ACTH in tumour tissue could be demonstrated only by radioimmunoassay. The negative results of the bioassay could be attributed to the relative insensitivity of the method used, and a similar explanation may account for the negative results using the immunofluorescence technique. Plasma levels of both calcitonin and ACTH were very high. A final diagnosis of an ACTH and calcitonin secreting medullary carcinoma of the thyroid was made. There is no reason to believe that these polypeptide hormones are produced by different cell types.