Pituitary xanthomatous lesions (which includes xanthomatous hypophysitis and pituitary xanthogranuloma) are rare sellar/suprasellar lesions, which are often only diagnosed postoperatively and present a diagnostic challenge as they are difficult to differentiate from other sellar lesions such as craniopharyngiomas and Rathke cleft cysts. In fact, it is likely that at least some of these lesions represent a reaction to leakage of and/or hemorrhage into a Rathke cleft cyst.
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Epidemiology
Xanthomatous lesions of the pituitary are rare with only case reports and series reported; roughly 0.6-2% of pituitary tumors 1,2
A female predilection has been reported (~2:1 female to male ratio), and generally, adolescents or young adults are affected 2-4.
Clinical presentation
The majority of the patients present with 2:
visual field symptoms due to local mass effect on the optic chiasm
endocrinological dysfunction due to compression on the pituitary stalk (most commonly hyperprolactinemia and hypoadrenalism)
headache
Pathology
Pituitary xanthomatous lesions have traditionally been divided into two groups: xanthomatous hypophysitis and xanthogranuloma based upon histology, although overlap exists 4.
Xanthomatous hypophysitis 4:
foamy histiocytes
lymphoplasmacytic infiltrate
CD68 positivity
little if any hemosiderin pigment
Xanthogranulomas 2,4:
necrosis and chronic inflammation
foamy xanthoma macrophage infiltration
lymphocytic infiltration
multinucleated giant cells
hemosiderin
cholesterol clefts
The emerging consensus appears to be supporting the idea that xanthomatous and xanthogranulomatous conditions of the pituitary and sellar region most likely represent a continuum of reaction to complications of underlying pituitary lesions, most frequently Rathke cleft cysts 4.
Radiographic features
The lesions commonly expand the sella, appear cystic and have a degree of enhancement (peripheral or homogeneous). They are hyperintense on T1-weighted images likely due to cholesterol component 2.
Calcification has been reported in some cases 5. Cavernous sinus invasion has not been reported 2.
Treatment and prognosis
Neither treatment nor complications are specific to these conditions but rather represent the management of benign mass lesions of the pituitary. Total surgical resection is the gold standard treatment and visual function prognosis is generally excellent. However, there is a high rate of postoperative hypopituitarism 2.
Differential diagnosis
Rathke cleft cyst: no solid or enhancing component
craniopharyngioma: no gender difference, tend to calcify
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