Medullary carcinoma of the thyroid

The results of our study may be summarized as follows: 1. Medullary carcinomas of the thyroid are derived from the C cells of the gland and are characterized by strong histologic and cytologic pleomorphism with inconstant stromal amyloid deposits. 2. The decisive morphodiagnostic criterion is immunohistochemical evidence of calcitonin coinciding with negative TG reactivity. 3. In addition to obligatory calcitonin expression, MCs may show variable synthesis of several polypeptids and biogenic (?) amines. 4. The varying immunoreactivity patterns are not related to the clinical behavior of the respective tumors. 5. Leu-M-1 antigen, a monocyte-granulocyte marker known to express in Reed-Sternberg cells and in certain nonhemopoietic neoplasms, can also be demonstrated in MCs. Leu-M-1 immunoreactivity was found to correlate significantly with an unfavorable course. Thus, the introduction of immunostaining for Leu-M-1 in cases of thyroid carcinoma may provide significant prognostic information for these patients.