Answer and Discussion of Quiz Set: U-001

2.    All of the following statements are true regarding the pharyngeal pituitary except which one?

A.  Its volume is about 1/1000 the volume of nomral anterior pituitary.

B.  The histologic component is identical to that of the anterior pituitary.

C.  Pituitary adenoma can arise from pharyngeal pituitary.

D.  It is located at the vellecula just anterior to the epiglottis.

Answer and Discussion: The answer is (D). The anterior pituitary is derived from the Rathke's pouch of ectodermal origin in the hard palate . It migrates upward through the cranpharyngeal canal. The pouch eventuallo loses its connection with the pharynx and fuses with the neurohypophysis originating from the neuroectoderm. The pharyngeal pituitary is best interpreted as a vestige of pituitary tissue in the palate during fetal development. They are located in the palate, often in the midline, that is under the former craniopharyngeal canal. It is not unusual that they deviate from the midline but most of them are within the lateral diameter of the pituitary gland. The majority of pharyngeal pituitary were found in the anterior pharyngeal roof, but some were found in the soft tissue just under the sella turcica or in the posterior pharyngeal roof. Pharyngeal pituitary exists life-long in every individual and is about 1/1000 of the of the normal anterior pituitary. The histologic component is very similar to that of normal anterior pituitary. Most of the ectopic pituitary adenomas in the literature are found in the sphenoid sinus/nasopharyngeal/clivus. This corresponds exactly to the locations of pharyngeal pituitary. The origin of the these ectopic pituitary adenomas can be be reasonably speculated as pharyngeal pituitary, although another origin, such as the craniopharyngeal canal, cannot be excluded.

Further Reading:

Hori A, Schmidt D, Rickels E.  Pharyngeal pituitary: development, malformation, and tumorigenesis. Acta Neuropathol. 1999 Sep;98(3):262-72.