Medullary carcinoma of the thyroid: histomorphological, histochemical and immunohistochemical analysis of twenty cases.

Histomorphological patterns of twenty primary medullary carcinomas of the thyroid were studied by light and polarized microscopy in relation to the content of calcitonin and thyroglobulin determined by the immunoperoxidase method: Out of 20 tumors, 10 showed classical, 7 glandular and 3 insular histomorphological pattern. In 19/20 cases, the cytoplasm of tumor cells contained various amounts of calcitonin, and the intensity of Immunoreaction was strong in 2/19, moderate in 7/19 and weak in 10/19 cases. Tumor stroma contained calcitonin in 7/20 cases. In 1/20 case, which did not show calcitonin immunoreactivity in the cell cytoplasm, the stroma contained a considerable amount of calcitonin. Thyroglobulin immunoreactivity was found in 4/20 tumors, 2 of them with classic and 2 with glandular histomorphological picture only in the cytoplasm of tumor cells. These tumors are considered medullary carcinomas with thyroglobulin immunoreactivity, since they do not fulfil the WHO criteria for "mixed medullary-follicular carcinomas".