Distribution of calcitonin- and somatostatin-containing cells in thyroid lymphoma and in Hashimoto's thyroiditis.

Eleven cases of thyroid lymphoma were studied by the immunoperoxidase avidin-biotin technique with calcitonin and somatostatin rabbit antisera. In 6 cases of non-Hodgkin lymphoma, in thyroid tissue residual to the lymphomatous infiltration, the C cell density was markedly increased and clustering was often observed; the C cells often took part in the follicular lining, frequently with polar distribution; these elements displayed a strong positivity for calcitonin, while the number of somatostatin-containing cells was lower and the staining less intense. In the only case of Hodgkin's lymphoma of the thyroid gland the staining was negative; in other 4 cases of non-Hodgkin lymphoma no residual thyroid tissue was found and the staining was also negative. As Hashimoto's thyroiditis is often associated with thyroid lymphoma, 13 cases of Hashimoto's thyroiditis were also studied; no C cells were observed and both stainings were negative. These data show that an increase in the C cell number may be a hallmark of thyroid lymphoma and that hyperplastic C cells show an intensive positivity for calcitonin. On the other hand, C cell hyperplasia is not present in Hashimoto's thyroiditis, in spite of the close association with thyroid lymphoma. Furthermore, we provide evidence that somatostatin-containing cells are present both in normal thyroid glands and in thyroid lymphoma.