An Immunohistochemical Study of Calcitonin–containing Cells in Benign and Malignant Thyroid Lesions

Parafollicular cells (C-cells) in benign and malignant thyroid lesions were studied immunohistochemically with a polyclonal anti-calcitonin (CT) antibody. The C-cells were seen most frequently in the middle third of the lateral lobes in the thyroid gland of normal individuals and patients with Graves' disease and chronic thyroiditis, although in the latter the number of such cells was significantly decreased (p less than 0.05). In adenomatous goiter, C-cells were present in nodular lesions from an early stage of nodule development (frequency about 19%), whereas in the later stage these cells were rarely observed inside type 1 nodules, which were generally characterized by an admixture of follicles with considerably different sizes. However, C-cells were not observed inside type 2 nodules, which were composed of similar-sized follicles, or in the parenchyma of 56 cases of benign and malignant thyroid tumors. These findings suggest that since C-cells are present in nodular lesions, the histogenesis of adenomatous goiter is quite different from that of follicular adenoma; thyroid neoplasms generally contain no C-cells in the parenchyma.