Intrathyroidal Thymic Tissue: An Autopsy Study in Fetuses with Some Emphasis on Pathological Implications

Abstract

Fifty-eight human thyroid glands obtained at autopsy from fetuses with proven retrosternal thymus were systematically studied for the presence of intrathyroidal thymic tissue. The latter was found in one thyroid lobe in each of three fetuses (5.1%). It was located in a subcapsular position in two cases (3.4%) and lying deep in thyroid tissue in one (1.7%). Our findings would support a IV-V pharyngeal pouch origin for some accessory thymic tissue and would provide an explanation of the histogenesis of intrathyroid thymomas.

Key Words:

• thyroid
• thymus
• fetus
• thymoma