The unusual presence of aberrant parathyroid and thymus tissue found in a child's pharynx recently at the Children's Hospital aroused our interest in the possibility of similiar cases and the circumstances in which they were found.
Embryologically the parathyroid glands arise from the dorsal branchial pouches III and IV. In the development of the embryo the parathyroid III moves more caudad than parathyroid IV, and both are usually found at the level of the thyroid gland at the latter's final position in the neck. The thymus develops from the ventral portion of the pouches III and IV, and in a similiar manner migrates to the superior mediastinum during fetal life.
Aberrant thymus tissue has been reported a number of times in the literature, its most frequent ectopic site being in the neck. Gilmour1 describes 13 cases of aberrant thymus tissue he had found in the neck, usually in intimate