Ephidermoid thyroid carcinoma is arare entity which was not accepted as a primary tumor of the thyroid gland until a few decades ago . It attain less than 1% among all of the maligns neoplasms of this gland. Because of its low incidence, not well known
and very discussed etiology. We decided to present two cases studied and operated on, in our institute.
We reviewed the literature and we give our opinions related to its probable etiology. (Oncología (Ecuador)
1996;6:324-327)

Key Words: Thiroid ephidermiod carcinoma, Embryology, Ephithelial sol id nests epithelial.