[Value of immunohistochemistry in the study of medullary cancer of the thyroid. Implications of the results for the concept of the APUD system and of apudomas].

Immunohistochemical studies in medullary thyroid carcinoma demonstrate the presence of C cells secreting calcitonin but also of other cells secreting other peptides or proteins. These different cells exist in the tumor as well as in metastases. These results and other reported in the literature suggest a common ultimobranchial and endodermal origin for these cells.