Abstract

We report a medullary carcinoma of the thyroid gland with a coexisting occult sclerosing papillary carcinoma. This rare case, in that the two types of carcinoma are completely separated and not intermixed together, is different from the previously reported mixed follicular and parafollicular cell carcinomas of the thyroid gland, so-called "differentiated thyroid carcinoma, intermediate type". The two separate tumors of the present case are undoubtedly of coincidental double primaries, and it can be a assumed that at least some of the mixed follicular and parafollicular cell carcinomas are results of collision of carcinomas derived from two embryogenetically different cell types.

• Keywords: Thyroid gland;Thyroid carcinoma;Medullary carcinoma;Papillary carcinoma;