[Immunohistochemical and ultrastructural study on medullary carcinoma of the thyroid].

Thirty seven cases of medullary carcinoma of the thyroid were studied by immunohistochemical technique and transmission electron microscopy (TEM). No amyloid deposit was observed in the tumor tissue in 6 cases. The monoclonal antibodies used were those directed to calcitonin, S-100, NSE and thyroid globulin. Their positive rates in the cancer cells were 100.0%, 45.9%, 64.9% and 16.2%, respectively. In the amyloid area, it was 89.3%, 25.0%, 35.7% and 14.2%. Many neurosecretory granules were found in the cytoplasm in 4/4 as observed by TEM. This study shows that the presence of calcitonin is of great value in establishing the diagnosis of medullary carcinoma. The results suggest that this tumor may arise from the parafollicular cells of the thyroid.