Mucosubstances in medullary carcinoma of the thyroid.

We have studied mucosubstances in 12 cases of medullary carcinoma of the thyroid using histochemical techniques and a number of different lectins. Immunohistochemical staining for calcitonin and carcinoembryonic antigen was also performed. We have found that the presence of mucosubstances is a constant finding in medullary carcinomas; they were present extracellularly in 100% of cases and intracellularly in 53.3%. In both these compartments there was a predominance of neutral over acid mucosubstances. Receptors for UEA-I, Con A, RCA-I, Succ-WGA and SBA were found in many cells in the majority of cases, but there were differences in the affinity from one case to another. Because of this lack of specificity lectin histochemistry is not of diagnostic value in medullary carcinomas of the thyroid. The possible relationships of the lectin-binding results to glycosylated hormone precursors and carcinoembryonic antigen are discussed.