Cervical Thymoma Head and Neck Service of Heliópolis Hospital (HOSPHEL), São Paulo, Brazil

The thymus is a gland originating from the epithelium, which forms in the third portion of the pharynx during the tissue matching that takes place in the sixth week of fetal life. In the eighth week of fetal life there is a migration of the thymus from the cervical region towards the caudal and medial region to its final location at the upper mediastinum. Failure of this migration will cause abnormalities of thymic tissue such as hypoplasia, cysts, glandular tissue at the periphery of the thyroid and cervical thymus with or without mediastinal extension. Thymic tissue with atypical location has been classified 3 into seven types: type 0, with no cervical extension; type 1, right or left extension, without contact with the thyroid gland; type 2, left or right extension in contact with thyroid; type 3, bilateral extension without contact with thyroid; type 4, bilateral extension, one side in contact with thyroid; type 5, bilateral ABSTRACT