USMLE Answer 33

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33. The correct answer is D. The tumor described is a craniopharyngioma, which is one of the more common brain tumors of children. These tumors arise from epithelial rests derived from Rathke’s pouch, which is an oral invagination that gives rise to the cells that form the anterior pituitary gland. Histologically, craniopharyngiomas can resemble ameloblastomas, which are tumors derived from dental epithelium.

Note that this question could also have been answered very simply by noting that the hypothalamus, pineal gland, pituitary gland, and the superior colliculus are all adult structures; only Rathke’s pouch is an embryonic structure. Therefore, only Rathke’s pouch could be the source of epithelial rests, which are remnants of embryonic tissues that persist in the adult.

Although craniopharyngiomas often occur near the hypothalamus (choice A) and posterior portion of the pituitary gland (choice C), they do not arise from neural tissue.

The pineal gland (choice B) and superior colliculus (choice E) are found on the posterior aspect of the brain stem.