Increase in S-100b protein content in thyroid carcinoma.

S-100b protein was detectable in the soluble fraction of thyroid tissue. The concentration of S-100b protein in thyroid carcinoma tissue was three to five times higher than in normal thyroid tissue and thyroid adenoma. It is, however, not higher in the thyroid tissue of Graves' disease. The increase of S-100b protein concentration was not remarkable in carcinomatous tissue of the stomach and other digestive organs. The calmodulin content in the thyroid carcinoma tissue increased but the increment was low compared to that of S-100b protein. These data suggest that S-100b protein may play a significant role in cell maturation or differentiation.