BILATERAL THYROID AND ULTIMOBRANCHIAL MEDULLARY CARCINOMA

The ultimobranchial bodies in human embryos develop from the fourth an d fifth branchial pouch complexes along with thymic and parathyroid ti ssue. They become incorporated within the lateral thyroid lobes and ar e believed to be involved in the development of C-cells. We report a c ase of an unusual bilateral thyroid and neck prelaryngeal medullary ca rcinoma in a 23-year-old male patient who belongs to a multiple endocr ine neoplasia type 2a (MEN type 2a) family with thyroid tumors and phe ochromocytomas. The medullary carcinoma was located in an abnormal cys tic structure that seems to be a remnant of the ultimobranchial body ( UBB) in the neck. Within the contralateral thyroid lobe, the medullary carcinoma was associated with C-cell hyperplasia.