IMMUNOHISTOCHEMISTRY OF MEDULLARY-THYROID CARCINOMA AND C-CELL HYPERPLASIA BY AN AFFINITY-PURIFIED ANTI-HUMAN CALCITONIN ANTISERUM

Background. The diagnosis of medullary thyroid carcinoma (MTC) depends on the calcitonin immunohistochemistry. Familial MTC is associated wi th C-cell hyperplasia (CCH), whereas sporadic MTC is not. A specific a nd sensitive calcitonin immunohistochemistry is necessary for the diag nosis of MTC and CCH. Methods. An affinity-purified anti-calcitonin an tiserum (APxCT) was used for immunohistochemistry of the thyroids of 1 5 patients with MTC. The thyroids of five patients with familial MTC w ere studied in detail, with each gland sectioned in 48 areas. Results. Between three and ten independent MTC were found in each thyroid, and CCH was found in all five patients (24.2%, varying from 8.4-56.3% of the 48 areas from each thyroid). MTC and CCH were localized mainly in the middle third and in the central axis of the thyroid lobes. They of ten were found together in the same area (in a total of 21 areas for t he five thyroids sectioned in 48 areas) but ten areas with MTC did not have CCH, and 37 areas with CCH did not have MTC. In ten thyroids par tially studied, CCH was indicated in three patients thought to have sp oradic MTC. In two thyroids, with follicular and papillary carcinoma, a higher density of C-cells was found around the tumors, but disease w as not characterized as CCH. Conclusions. APxCT antiserum increased th e immunohistochemical specificity and sensitivity. The distinction of the familial from the sporadic MTC requires a careful and extensive se arch of CCH. C-cells in high density may be found around follicular ce ll carcinomas, being a potential source of diagnostic error.