If you’re preparing for the United States Medical Licensing Examination® (USMLE®) Step 1 exam, you might want to know which questions are most often missed by test-prep takers. Check out this example from Kaplan Medical, and read an expert explanation of the answer. Also check out all posts in this series.
A five-year-old girl is brought to the physician by her parents because of short stature. The girl has complained to her parents about headaches almost daily. Funduscopic examination shows papilledema and visual field testing shows bitemporal hemianopia. CT scan shows a 3-cm intracranial mass with foci of calcification. Surgical resection is performed. Gross examination shows a multiloculated cystic and solid tumor containing dark brown, oily fluid. The resected tumor most likely originated from which of the following structures?
A. Hypothalamus
B. Pineal gland
C. Posterior pituitary gland
D. Rathke's pouch
E. Superior colliculus
The correct answer is D.
Kaplan Medical explains why
The patient has a craniopharyngioma. Bitemporal hemianopia, calcification on CT, and resection showing a cystic mass containing dark brown oily fluid all point to this diagnosis. Craniopharyngiomas arise from remnants of Rathke’s pouch.
Why the other answers are wrong
Choice A. This patient's signs, symptoms, and pathology results are typical of a craniopharyngioma, which arises from remnants of the Rathke's pouch. Hypothalamic tumors are usually gliomas, which are typically more solid and do not contain dark brown, oily fluid.
