Table 2.

Imaging key points of pituitary tumors and tumor-mimicking lesions

PitNET/pituitary adenoma	• Signal intensity on MRI varies, because components, such as water, are not constant, and modifications, such as degeneration, hemorrhage, and infarction, also develop • Contrast-enhanced T1WI often shows mildly hypointensity compared to the normal pituitary glands • Has a later peak of contrast than the normal pituitary on dynamic MRI • Dynamic MRI is most useful in localizing microadenomas • Macroadenomas often shows a snowman shape • Macroadenomas may compress the optic chiasm and optic nerve, or involve the cavernous sinus • Macroadenomas can present as cystic masses with fluid–fluid level reflecting hemorrhage • Densely granulated somatotroph PitNET/pituitary adenoma shows hypointensity compared to the gray matter on T2WI
Adamantinomatous craniopharyngioma	• Often occurs in the suprasellar region • Typically contains both cystic and solid components • The cystic component shows hyperintensity on T1WI • The cyst wall exhibits contrast enhancement and shows annular or nodular calcification
Papillary craniopharyngioma	• 2/3 are found in the third ventricle and 1/3 in the infundibulotuberal regions • Spherical and solid with uniform contrast enhancement • Presents with a duct-like recess at the base of the mass
Pituitary blastoma	• Occurs primarily in infants • Solid tumor with a small internal cystic component • Similar presentation to macroadenoma
Pituicytoma	• Isointensity on T1WI and isointensity on T2WI to gray matter • Uniform and strong contrast enhancement • Flow voids may be prominent around the tumor
Pituitary glioma	• Grade 2 astrocytoma is common
Pituitary gangliocytoma	• Usually occurs as a mixed gangliocytoma-PitNET/pituitary adenoma • Cannot be distinguished from PitNETs/pituitary adenomas
Sellar atypical teratoid/rhabdoid tumor (AT/RT)	• Occurs in adults and mostly in women • Similar presentation to macroadenoma
Germinoma	• Found in the hypothalamus, pituitary stalk, and posterior pituitary gland • CT shows high density to gray matter • Contrast-enhanced T1WI shows a uniform contrast enhancement • DWI shows hyperintensity
Meningioma	• Purely intrasellar meningiomas are rare • Presents with a normal (compressed) pituitary gland • CT may show calcifications within the tumor, bony hyperostosis, or an enlarged sphenoid sinus (pneumosinus dilatans) in adjacent regions • Contrast-enhanced T1WI shows a uniform contrast enhancement • Dural tail is frequently observed
Chordoma	• CT shows extensive lytic bone destruction • On T2WI, conventional chordoma typically shows marked hyperintensity • Contrast-enhanced T1WI shows moderate-to-marked contrast enhancement, and may appear a “honeycomb” enhancement pattern • ADC of conventional chordomas is about 1.5 × 10–3 mm2/s Poorly differentiated chordoma often shows hypointensity on T2WI compared to conventional chordomas
Metastatic tumors	• May present as a dumbbell-shaped tumor • Sellar bone erosion may be seen but not sellar enlargement
Lymphoma	• Contrast-enhanced T1WI shows a uniform contrast enhancement • DWI shows hyperintensity • The cavernous sinus is involved in approximately 40% of cases
Pituitary abscess	• Cystic lesion within the pituitary gland • Marked hyperintensity on DWI • Contrast-enhanced T1WI shows rim-like contrast enhancement • Often shows thickening of the pituitary stalk, predominantly in the inferior region
Hypophysitis	• Symmetrical enlargement of the pituitary gland and stalk • Contrast-enhanced T1WI shows a uniform contrast enhancement • Loss of hyperintensity in the posterior pituitary gland on T1WI • Thickening of the of the surrounding dura mater (dural tail) may be observed • Hypointense regions on T2WI of the peripituitary region (parasellar T2-dark sign) may be observed
Pituitary hyperplasia	• Often shows homogeneous intensity and contrast enhancement on MRI
Rathke’s cleft cyst	• Usually occurs between the anterior and posterior lobes of the pituitary gland • Often shows hyperintensity on T1WI • Characteristic intracystic nodules reflecting waxy component (so-called waxy nodule) may be observed • The cyst wall usually has non-contrast enhancement
Arachnoid cyst	• T1WI and T2WI show a thin-walled cyst with a homogeneous signal equal to that of the cerebrospinal fluid • Arachnoid cyst within the sella turcica tends to push the pituitary gland posteriorly
Aneurysm	• CT and MR angiography aid in diagnosis • Hypointense on T2WI due to flow void • Thrombosed areas show hyper-or heterogeneously intense signals on T1WI • The intensity can be altered by calcifications, lamellated blood degradation products, and flow-related signals

MRI magnetic Resonance imaging; T1WI T1-weighted image; T2WI T2-weighted image; CT computed tomography; DWI diffusion-weighted imaging; ADC apparent diffusion coefficient