The origin of the median anlage of the thyroid gland as a diverticulum from the mesobranchial region of the pharyngeal floor, which lies between the ventral extremities of the first two gill pouches, was conclusively demonstrated by Norris1 in a study of human embryos. According to Joll,2 maldevelopment of the median anlage is known to give rise to a variety of abnormalities, which may be located in the midline from the foramen caecum to the level of the suprasternal notch. They include solid tumors, cysts, sinuses and fistulas. A solid tumor of the thyroglossal tract is most common in the region of the foramen caecum, although microscopic amounts of thyroid tissue may occur in any part of the primitive tract. Such a tumor usually consists of well differentiated thyroid tissue and constitutes a lingual thyroid. Ray3 collected 250 cases of this condition recorded in the literature from
CROMARTIE WJ, NELSON OG. ADENOCARCINOMA OF TONGUE ARISING FROM VESTIGE OF MEDIAN ANLAGE OF THYROID GLAND: RPORT OF A CASE. Arch Surg. 1941;43(4):599–608. doi:10.1001/archsurg.1941.01210160060009
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