Squamous cell carcinoma of the thyroid gland -- transition from adenocarcinoma.

Eight autopsy cases of thyroid carcinoma, in which adenocarcinoma and squamous cell carcinoma coexisted, and presented. In these adenosquamous cell carcinoma, pathological findings suggest direct transition from papillary adenocarcinoma to squamous cell carcinoma, rather than transformation to squamous cell carcinoma via squamous metaplasia. We believe that squamous cell carcinoma arises from adenocarcinoma of the thyroid in most cases.