[Demonstration in a thyroid cancer of vesicular structures similar to ultimobranchial-type vesicles described in mice].

An immunohistochemical and electron microscopy study has allowed us to find in a human thyroid cancer, follicle differentiation associating in a characteristic architectural pattern C cells, ciliated cells and follicular cells. Ultrastructural features were similar to those described in the normal adult Mouse thyroid by Wetzel and Wollman [1] and interpreted by them as a second type of thyroid follicle of ultimobranchial origin. The discovery of these structures within metastatic lymph nodes excludes normal thyroid follicle contamination. The presence of these neoplastic structures lead us to make the hypothesis of a stem cell of ultimobranchial and endodermal origin common to all the cells described.