Mount Sinai's Radiology Charts

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Author: Dairon Garcia
 NECT CECT MRI - T1 MRI - T2 MRI - Diffusion/ADC MRI - Post-contrast T1 Gross Pathology Histology Additional comments
Aneurysm -Patent aneurysm: • Well-delineated round/lobulated extra-axial mass • Slightly hyperdense to brain (may have mural Ca++).-Partially/completely thrombosed aneurysm: • Moderately hyperdense (Ca++ common) -Lumen of patent aneurysm enhances strongly, uniformly. - Completely thrombosed aneurysm may have reactive rim enhancement Variable. -Patent aneurysm (signal varies): • 50% have "flow void" on T1WI • 50% iso/heterogeneous signal. -Partially/completely thrombosed aneurysm: • Signal depends on age(s) of clot • Common = mixed signal, laminated thrombus

Heterogeneous signal intensity on both T1 and T2 weighted imaging is a distinctive feature of an aneurysm with a thrombosed component, whereas flow void indicates a patent aneurysm. 		Typically hypointense. May be laminated with very hypointense rim. Heterogeneous signal intensity on both T1 and T2 weighted imaging is a distinctive feature of an aneurysm with a thrombosed component, whereas flow void indicates a patent aneurysm. DWI: +/- Foci of restricted diffusion secondary to vasospasm, ischemia (no image available) Slow flow in patent lumen may enhance

Image 2 		Localized, blood-filled balloon-like bulge in the wall of a blood vessel. Mild atherosclerosis of the cerebral arteries might be seen as well as tortuous cerebral vessels.

Image 2 		Wall of the aneurismal sac composed of a thin layer of fibrous connective tissue. Muscle layer absent
Pituitary adenoma Microadenomas: If uncomplicated (no hemorrhage, cyst), microadenomas are isodense, invisible. Macroadenomas: Well-delineated round/lobulated extra-axial mass. Usually isodense with gray matter (typical). Cysts, necrosis common (15-20%). Hemorrhage (10%), Ca++ (1-2%). Invasive adenomas (see image): can show marked destruction of the sphenoid body, greater wings, and petrous apices. The soft-tissue mass can extend anteriorly along the sphenoid rostrum into the nasal septum. Macroadenoma: delayed moderate contrast enhancement of the solid portion of the tumor mass. Microadenomas (see image): 2/3 appear hypodense to normal pituitary on dynamic scans. Early images- hypodense. Progressive isodense. Delayed images- hyperdense. Abnormal height and upward convexity of the gland are reliable signs of prolactinoma; abnormal density and enhancement are suggestive signs.

Invasive adenomas: Contrast-enhanced scan shows an enhanced mass in the region of the sphenoid body. 		Microadenoma: Variable signal intensity, usually isointense with normal pituitary gland. Can be hyperintense if hemorrhage, necrosis.

Usually isointense with gray matter. Subacute hemorrhage (T1 shortening). Fluid-fluid levels may occur, especially with pituitary apoplexy. Posterior pituitary "bright spot" displaced into supradiaphragmatic level in 80% of cases. Posterior pituitary "bright spot" absent in 20% of large adenomas isointense relative to white matter 		Microadenoma: Typically isointense to normal pituitary gland.(no image available)

Macroadenoma: most commonly Isointense with gray matter. Less commonly with cysts (hyperintense), hemorrhage (signal varies with age), Densely granulated, growth-hormone-producing adenomas often hypointense. Uncommon: High signal along optic tracts, seen with 15-20% of adenomas that touch/compress optic pathway. (no image available) 		Restricted diffusion may be seen in the setting of vasospasm, ischemia. Restricted diffusion within adenoma may be early sign of apoplexy (no image available) Microadenoma: Relatively hypointense over the first 1 to 2 minutes after the injection. 70-90% relatively hypointense compared to intensely enhancing pituitary gland and cavernous sinus. Generally enhance but more slowly than adjacent normal pituitary.

Macroadenoma: delayed moderate contrast enhancement of the solid portion of the tumor mass Macroadenoma: hyperintense, can have relatively homogeneous enhancement when there is no necrosis or hemorrhage. Some macroadenomas (thyrotropin-secreting adenomas, necrotic adenomas) are hypoenhancing Subtle/mild dural thickening ("tail") present in some cases. 		Microadenoma: Small reddish-pink nodule. (no image available)

Macroadenoma: Reddish-brown, lobulated mass. "Capsule" of macroadenoma is normal compressed pituitary gland. Usual growth pattern: Bulges upward into suprasellar cistern. Gross cavernous sinus invasion at autopsy in 5-10%, microscopic in 45%. Invasive benign adenoma >> pituitary carcinoma (exceedingly rare). (no image available) 		Small oval or polyhedral cells in a sheetlike monomorphous array.Cellular pleomorphism, accasional mitoses (not indicate agressive behavior). Calcification is rare. When there is no necrosis, a so-called organoid pattern can be seen with nests of uniform epithelial cells that are divided by a network of delicate capillaries within fibrous strands.
     
Meningioma Slightly hyperdense to brain. Can arise from diaphragma sellae (thin black line separates mass from pituitary). "Dural tail sign" can be seen which is highly suggestive but not pathognomonic. Enhancing with typically sharp margins and homogeneous density.

Hyperostosis of parts of the sphenoid bone can be seen. 		Generally isointense relative to cortical gray matter on T1 weighted images. Signal variability may occur because of the presence of calcium, which results in lower signal intensity, or atypical features such as cystic components or hemorrhage. Hyperostosis may be evident as focally expanded bone, which may be hyperintense on T1 weighted images due to fatty marrow. Thickened cortical bone does not produce any signal and consequently may not be as easily appreciated. Generally isointense relative to cortical gray matter on T2- weighted images. Peritumoral edema is best detected on T2-weighted images. DWI, ADC maps for typical meningiomas (WHO grade 1) variable in appearance. Lower ADC in malignant and atypical meningiomas compared to typical (no image available) Contrast material enhancement of meningioma is usually rapid and striking owing to their highly vascular nature. Enhancement is commonly uniform. Meningiomas may demonstrate linear enhancement of the adjacent dura mater-the dural “tail” or “flare” sign. 2 basic morphologies: Globose = globular, well-demarcated neoplasm with wide dural attachment; and En plaque = sheet-like extension covering dura without parenchymal invagination. Homogeneous reddish-brown translucent pale surface.Soft to tough, occasionally gritty, Depends on fibrous tissue, Ca++ calcium content. Typical benign meningiomas usually invaginate into brain, do not invade it (Image not from suprasellar region, rather from right peripheral cerebral hemisphere. Shows vascular meningioma with dural attachment (arrowheads), fresh bleeding reflects hypervascularity of the tumor.). The histologic features of meningiomas are quite variable. Typical meningiomas consist of oval to elongated bipolar cells with eosinophilic cytoplasm that are arranged in syncytial configurations and occasional whorls. The round to oval nuclei appear histologically uniform and benign. Psammoma bodies (concentrically laminated calcifications) are a distinguishing feature when present.
 
Metastases Metastases more common in cerebral hemispheres (80%) than suprasellar region or pituitary. Typically iso or hypodense masses. The bone destruction and the soft-tissue components are best evaluated with the use of CT. Prostate gland metastases typically produce hyperostosis with an associated soft-tissue mass, which may be mistaken for a meningioma. Lung and breast metastases are generally lytic and may also have a soft-tissue component. (Axial CT scan demonstrates a destructive lesion involving the central skull base (arrow) in a patient with metastatic breast cancer.) Enhancement patterns include intense, punctate, nodular, or ring enhancement. Lytic and blastic metastatic lesions will generally demonstrate enhancement at CT (no image available) Iso- or hypointense mass. Metastases with intrinsically short T1 may be hyperintense (e.g., melanoma). Image shows metastases from squamous cell carcinoma of the sphenoid sinus.

Destruction of the sella and invasion of the suprasellar region can be seen (as in metastatic breast carcinoma). 		Usually hyperintense. Depending on the tumor type, T2 shortening may occur such as with hemorrhage or melanin which can produce heterogenous or low signal intensity. Reaction surrounding a lesion can be hyperintense. May mimic vascular disease if metastases scattered (no image available). isointense to slightly hyperintense on DW images. Signal intensity of nonnecrotic components of metastases on DW images is variable (generally iso- or hypointense; occasionally hyperintense). The necrotic components of metastases show a marked signal suppression on DW MR images and increased ADC values (no image available). Enhancement patterns include intense, punctate, nodular, or ring enhancement. Image 1 from metastatic breast Ca.

Delayed sequences can show additional lesions. 		Features can include round, confluent tan or gray-white mass, edema, local mass effect, and hemorrhage which is common in melanoma, choriocarcinoma, lung and renal cell carcinomas (no image available) Usually similar to primary, sually displaces brain parenchyma. Necrosis common, Neovascularity common. Marked mitotic figures. (Image shows metastatic squamous cell carcinoma, which is moderately well differentiated, containing sheets and nests of polygonal cells with dark, irregular nuclei. Keratinization of the cytoplasm is usually apparent). The hypophysis, infundibulum and tuber cinerium lack a blood brain barrier and are more vulnerable sites for hematogenous metastasis than brain parenchyma.

The cavernous sinus is also a site of hematogenous spread, but it may be involved by perineural extension along cranial nerves. The cavernous sinus and sella turcica can both be invaded by direct extension of nasopharyngeal tumors, usually squamous cell carcinoma.
   
Germ cell tumor CT demonstrates a sharply circumscribed, hyperattenuating mass. The increased attenuation is related to the highly cellular lymphocyte component within the tumor. Enhancing, ± cysts, hemorrhage. May have granular appearance. Hypo- to isointense to gray matter. Short T1 due to protein, blood, or fat. Homogeneous, well-marginated round solid masses that can involve the infundibular stalk and the floor of the third ventricle. iso- to slightly hyperintense with T2-weighted sequences. The short T2 relaxation time presumably reflects the diminished free water content of these tumors. DWI: ± restriction within solid components. Reduced diffusion is indicative of the highly cellular nature (no image available) Prominent and homogeneous enhancement.

Prominent and homogeneous enhancement (image shows fat suppressed sequence depicting a solid mass with a cystic area.) 		Soft, often friable mass (no image available) Germinomas are well-circumscribed lesions that demonstrate a two-cell pattern of lymphocytes and large polygonal primitive germ cells. The abundance of lymphocytes contributes to the hyperattenuation seen at CT and the reduced diffusion at diffusion-weighted MR imaging. Germinomas can be divided into two subtypes: pure germinoma and germinoma with syncytiotrophoblastic cells. Those containing syncytiotrophoblastic giant cells have a higher recurrence rate and decreased long-term survival and demonstrate elevated CSF levels of hCG

Image 2 		Suprasellar germinomas are characterized by homogeneity and the lack of cystic and calcific components. Typically, the high signal intensity of the posterior pituitary lobe will not be seen on sagittal T1-weighted images due to blockage of the infundibulum by the mass.
   
Granuloma Tuberculoma is hypodense to hyperdense round or lobulated nodule/mass with moderate to marked edema Ca++ in approximately 20% (no image available) Tuberculoma: Solid or ring-enhancing. "Target" sign: Central Ca++ or enhancement surrounded by enhancing rim (no image available). The granulomatous lesion is usually isointense on T1(no image available). The granulomatous lesion is usually isointense to hyperintense on T2-weighted images. Noncaseating granuloma: Hyperintense to brain. Caseating granuloma: Hypointense rim. Surrounding edema common. May show hyperintense center of tuberculoma. Helpful for detecting complications such as stroke, cerebritis (no image available). Noncaseating granuloma: Nodular, homogeneous (image shows sarcoid)

Caseating granuloma: Peripheral rim enhancement. (image shows tuberculoma with diffuse irregular enhancement) 		Noncaseating/ caseating with solid center, or caseating with necrotic center (no image available). small granulomas consisting of well-demarcated collections of epithelioid histiocytes with admixed, multinucleated giant cells and small numbers of lymphocytes

Although the granulomas in tuberculosis are typically larger with a central area of necrosis, these latter features are not specific. Special stains and cultures for acid-fast bacilli as well as fungi are required for diagnosis (image shows TB) 		When tuberculosis and sarcoidosis involve the central nervous system, they may occur as suprasellar masses with thickening of the infundibulum and optic chiasm.
The preferential involvement of the basilar cisterns may lead to a vasculopathy of the small arteries in the anterior and posterior perforating substances. As a result, deep white matter and basal ganglion infarcts may result.
           
Arachnoid cyst Usually CSF density. Hyperdense if intracyst hemorrhage present rarely. May expand, thin/remodel bone (no image available). Does not enhance (no image available). MR images depict a smoothly marginated mass that is isointense relative to cerebrospinal fluid with all spin-echo sequences. The extra-axial origin, degree of mass effect, and cyst extension are accurately depicted. Vasogenic edema is not a feature of this lesion. Isointense with CSF No restriction (no image available). Does not enhance (no image available). Fluid-containing cyst with translucent membrane. Arachnoid layers bulge around, contain CSF collection (no image available). Wall consists of flattened but normal arachnoid cells. No inflammation or neoplastic change. (image shows thin cyst wall composed of collagen and a lining of flattened arachnoid cells). CSF fluid collections, most common in middle cranial fossa (50-60%) and suprasellar cistern (10%). Congenital or acquired.
         
Craniopharyngioma Adamantinomatous type (cystic in childhood):90% mixed solid (isodense), cystic (hypodense) 90% calcify, 90% enhance (solid = nodule; rim = capsule). Papillary type (solid in older adults): Often solid, isodense, rarely calcifies. (Image shows: A. Conventional CT scan (8-mm collimation) reveals no low-attenuation coefficient mass. The anterior portion of the suprasellar cistern is poorly defined. B. An intravenous enhanced scan (8-mm collimation) shows no mass enhancement. The basilar artery (B) and other basal arteries are seen.) Intense and uniform enhancement of the noncalcified solid components. (Image shows: A. Conventional CT scan (8-mm collimation) reveals no low-attenuation coefficient mass. The anterior portion of the suprasellar cistern is poorly defined. B. An intravenous enhanced scan (8-mm collimation) shows no mass enhancement. The basilar artery (B) and other basal arteries are seen.) Heterogenous, Signal varies with cyst contents. Calcification-hypointense. Cystic moiety may have high cholesterol content or contain hemorrhage, both hyperintense. Solid components moderate T1 signal.

Image 2 		Cystic areas hyperintense. Solid components vary from hypo to midly hyperintense. Variable depending upon character of cyst fluid (no image available). The solid portions enhance heterogeneously. The thin walls of the cystic areas nearly always enhance. Solid tumor with variable cysts. Adamantinomatous cysts often contain thick "crankcase oil" fluid. Epithelial fronds penetrate adjacent hypothalamus/chiasm. (no image available). characteristic histologic appearance. There is a complex pattern of epithelial growth consisting of cords and islands of squamous cells surrounded by a layer of tall basaloid cells). These proliferating epithelial cells are surrounded by fibrous stroma. Foci of calcification and cystic structures with necrotic debris are commonly present. The histopathologic features of craniopharyngiomas are quite variable, and this is reflected in their imaging characteristics, they are the most heterogeneous of all sellar and suprasellar lesions encountered in MR imaging. These tumors often have both cystic and solid components.
   
Rathke's cleft cyst Well-delineated round/lobulated intra/suprasellar mass. 75% hypo-, 25% mixed iso/hypodense. 10-15% Ca++ (curvilinear, in cyst wall). No enhancement Varies with cyst content (serous vs mucoid). 75% Hyper- vs 25% hypointense. 75% hyperintense intracystic nodule. 5-10% mixed (may have fluid-fluid level) Varies with cyst content. 50% moderate to strong hyper-, 25% iso-, 25% hypo-. 75% hypointense intracystic nodule. No restricted diffusion (image not available) Not enhancement. 75% small nonenhancing intracystic nodule. (no image available). Smoothly lobulated, well-delineated cystic mass. Content varies from clear CSF-like fluid to thick mucoid material. (no image available). Wall: single layer of ciliated cuboidal/columnar epithelium, +/- globet cells. Variable cyst content: clear or serous, +/-hemorrhage. Amorphous, inspissated eosinophilic mucicarmine-positive colloid +/- cholesterol cleft. Firm, waxy yellow, inspissated material. (image shows stratified squamous epithelium with orderly maturation and mucin-containing cells(arrow) staining red.) benign cystic sellar lesions. generally asymptomatic.
     
Hypothalamic glioma Tissue density mass. Focal hypodensity if cystic spaces. (Image shows hypothalamic glioma with exophytic extension, non-contrast study. The suprasellar cistern is entirely obliterated by a tissue-density mass (arrow head) measuring 10-17 H. The brain stem is rotated and the temporal horns are dilated, arrow) Enhancement. (Image shows axial CT, reverse mode: asymmetric enlargement of the right optic nerve by a glioma (30 H) on an unenhanced scan. B and C. Axial CT and coronal brain scans, standard mode: huge intracranial component of the right optic nerve glioma in the chiasmatic and hypothalamic areas (arrows) after contrast enhancement, 57H.) Isointense to mildly hypointense compared to brain. Focal hypointensity if cystic spaces present.

Isointense to mildly hypointense compared to brain. Focal hypointensity if cystic spaces present 		Signal is variable, but moderate hyperintensity typical. Peripheral hyperintensity due to perineural arachnoid gliomatosis (PAG) in NF1. Focally hyperintense cystic spaces of mucinous degeneration in sporadic cases (image shows involves the optic chiasm and extends to the right optic nerve,arrowheads) Elevated mean ADC values have been demonstrated (no image available). Enhancement varies from minimal to intense. Syndromic: Often little enhancement. Sporadic: Moderate to intense enhancement. Adult: Moderate heterogeneous enhancement. Dynamic contrast-enhanced (DCE) MR: Increased mean permeability values demonstrated in clinically aggressive tumors. When extending to optic nerve there is diffuse optic nerve enlargement; tan-white tumor. Cystic component related to mucinous degeneration or infarction. Childhood lesions with NF1: Tubular, tortuous. Childhood lesions without NF1: Rounded, cystic changes (no image available). Features of low-grade astrocytoma. Spindle-shaped astrocytes with hyperplasia of adjacent fibroblasts and adjacent meningothelial cells. Syndromic: Circumferential perineural infiltration with arachnoid gliomatosis. Central nerve sparing (relatively preserved vision). Sporadic: Expansile intraneural infiltration. Adult: Anaplastic astrocytoma or glioblastoma multiforme (image shows astrocytic proliferation with nuclear hyperchromasia and mild to moderate pleomorphism (grade 2), arrows). Distinction between hypothalamic and optic glioma tumor types is arbitrary because the point of origin cannot usually be defined. Presentation before age 5 years favors the diagnosis of glioma, as does an association with cutaneous or radiologic stigmata of NF-1. Gliomas of the optic chiasm and hypothalamus account for 10%–15% of supratentorial tumors in children.
   
Optic chiasm glioma Optic gliomas involving the chiasm may present as anterior suprasellar masses indenting or filling in the suprasellar cistern similar to pituitary adenomas. In the absence of frank suprasellar mass, asymmetry of the anterior portion of the suprasellar cistern, i.e., unilateral splaying of the anterior portion of the star, is a strong clue to the presence of unilateral intracranial extension of optic and perioptic tumors. Isodense fusiform nerve enlargement can be seen, focal hypodensity if cystic spaces. Bone CT can show Ca++ rarely (unlike optic nerve sheath meningioma). Enlargement of bony optic canal if intracranial extension. (image shows: Intracranial extension of right optic gliomas (2 patients). A. Enlargement of the right optic nerve (.) at its junction with the chiasm indicates intracranial optic or perioptic mass B. In this patient with known optic glioma, asymmetry of the anterior portion of the star with splaying of the contour on the right also indicates intracranial extension. Enhancement. (Image shows axial CT, reverse mode: asymmetric enlargement of the right optic nerve by a glioma (30 H) on an unenhanced scan. B and C. Axial CT and coronal brain scans, standard mode: huge intracranial component of the right optic nerve glioma in the chiasmatic and hypothalamic areas (arrows) after contrast enhancement, 57H.) Isointense to mildly hypointense compared to brain. Focal hypointensity if cystic spaces present. Signal is variable, but moderate hyperintensity typical. Peripheral hyperintensity due to perineural arachnoid gliomatosis (PAG) in NF1. Focally hyperintense cystic spaces of mucinous degeneration in sporadic cases (image shows involves the optic chiasm and extends to the right optic nerve,arrowheads) Elevated mean ADC values have been demonstrated (no image available). Enhancement varies from minimal to intense. Syndromic: Often little enhancement. Sporadic: Moderate to intense enhancement. Adult: Moderate heterogeneous enhancement. Dynamic contrast-enhanced (DCE) MR: Increased mean permeability values demonstrated in clinically aggressive tumors. When extending to optic nerve there is diffuse optic nerve enlargement; tan-white tumor. Cystic component related to mucinous degeneration or infarction. Childhood lesions with NF1: Tubular, tortuous. Childhood lesions without NF1: Rounded, cystic changes (no image available). Features of low-grade astrocytoma. Spindle-shaped astrocytes with hyperplasia of adjacent fibroblasts and adjacent meningothelial cells. Syndromic: Circumferential perineural infiltration with arachnoid gliomatosis. Central nerve sparing (relatively preserved vision). Sporadic: Expansile intraneural infiltration. Adult: Anaplastic astrocytoma or glioblastoma multiforme (image shows astrocytic proliferation with nuclear hyperchromasia and mild to moderate pleomorphism (grade 2), arrows). Distinction between hypothalamic and optic glioma tumor types is arbitrary because the point of origin cannot usually be defined. Presentation before age 5 years favors the diagnosis of glioma, as does an association with cutaneous or radiologic stigmata of NF-1. Gliomas of the optic chiasm and hypothalamus account for 10%–15% of supratentorial tumors in children.
   
Tuber cinerum hamartoma Homogeneous.Isodense or slightly hipodense to brain. Less common: cyst, Ca++. (Image shows CT scan at suprasellar level showing obliteration of the posterior suprasellar cistern). Nonenhancing. (image shows: C. CT scan with contrast showing obliteration of the suprasellar cistern by a mass which is not enhanced by contrast. There is possible lateral displacement of the posterior communicating arteries (arrows) as such displacement was demonstrated angiographically. D. 13 mm above the level of C showing deviation of anterior third ventricle to the right, arrow). Isointense or slightly hypointense to gray matter. Fat or cyst rare.

Image 2 		Iso or slightly hyperintense signal (occasionally very intense due to fibrillary gliosis). nonenhancing Mature neuronal ganglionic tissue project from hypothalamus, tuber cinereum or mamillary bodies. (Image shows cross-section of the brain tissue showing a large hamartoma in the left hypothalamus (arrows). OC = optic chiasm.) Heteropia. Resembles gray matter with neurons similar to hypothalamus. Myelinated/unmyelinated axons and variable amounts of fibrillary gliosis. Rare: cyst, calcification, necrosis and fat (no image available).
   
Dermoid Relatively homogeneous mass of low attenuation, similar to that of cerebrospinal fluid. Dermoid cysts are typically midline fatty masses in the sellar, parasellar, and frontonasal region, with only 20% having capsular calcification. Variable but generally no enhancement (no image available) Unruptured, the mass is typically hyperintense.If the mass does not contain sebaceous lipid material, it can appear as a homogeneous mass of low signal intensity, yet slightly brighter than cenebnospinal fluid.

In the setting of dermoid cyst rupture, multiple subarachnoid foci of high signal intensity consistent with fat accumulations can be seen anterior to and along the corpus callosum. 		Unruptured, the mass can appear heterogeneous in signal, but can be homogeneously hyperintense relative to brain tissue and isointense to cerebrospinal fluid. If ruptured, the droplets are typically hyperintense. Reduced diffusion (no image available) There can be mild enhancement of the capsule without central enhancement. Enhancement of the pituitary stalk and gland can be seen. Unruptured, the mass can appear heterogeneous in signal. If the mass does not contain sebaceous lipid material, it can appear as a homogeneous mass of low signal intensity, yet slightly brighter than cerebrospinal fluid. If ruptured, there can be extensive leptomeningeal enhancement possible from chemical meningitis. Yellowish mass in the middle, under the frontal lobes and anterior to the brain stem. Dermoid inclusion cysts are often called ‘buttery” tumors because of their yellow color and soft consistencv. Shows epidermal appendages, such as the pilosebaceous units, in association with an epidermal lining. essential difference between a dermoid cyst and an epidermoid cyst lies in the presence of skin appendages (eg, sebaceous glands, hair follicles) within the wall of the dermoid cyst and the absence of these features in the epidermoid cyst.
   
Epidermoid attenuation usually similar to CSF. Ca++ in 10-25%. Generally no enhancement on CT (no imaging available) Only slightly hyperintense to CSF on T1WI, slightly more hyperintense with heterogeneous signal intensity compared with CSF-containing arachnoid cysts.

Usually located in the sellar and suprasellar regions, the middle fossa, or off the midline in the posterior fossa.On long TR/TE sequences, these tumors show hyperintensity, similar to or greater than that of CSF. It is difficult to discern the exact extension of an epidermoid tumor with only T1-, T2-, or proton density-weighted imaging. 		The T2-weighted appearance of epidermoids is variable, ranging from hypointense to hyperintense with respect to gray matter, but they tend toward relative T2 prolongation. With FLAIR and diffusion-weighted pulse sequences, epidermoid cysts show higher signal intensity than does CSF, and thus can help in differentiating epidermoid cysts from arachnoid cysts or enlarged CSF spaces.

Diffusion Weighted 		No enhancement or minimal marginal enhancement (no image available) shiny 'mother of pearl' appearance to surface. Cyst contents appear soft, waxy flaky material Orderly stratified squamous epithelium with the normal maturation and keratinization and a surrounding capsule of collagen lining a central cystic region
       
Lymphoma Classically hyperdense; may be isodense, with or without hemorrhage, necrosis can be seen in immunocompromised (no image available) Enhancement is common in a moderate, uniform distribution in immunecompetent patients. Less commonly, there is ring-like distribution in immunocompormised patients. Rarely, there is no enhancement as can be seen in infiltrative lymphoma.(no image available) Immunocompetent: Homogeneously iso-/hypointense to cortex. Immunocompromised: Iso-/hypointense.May be heterogeneous from hemorrhage, necrosis (no image available) Immunocompetent: Homogeneously iso-/hypointense to cortex. Hypointensity related to high nuclear to cytoplasmic ratio. Immunocompromised: Iso-/hypointense. May be heterogeneous from hemorrhage, necrosis. Ca++ may rarely be seen, usually after therapy. Mild surrounding edema is typical. (no image available) May show restricted diffusion. Low ADC values compared to malignant glioma. (no image available) Immunocompetent: Strong homogeneous enhancement. Immunocompromised: Peripheral enhancement with central necrosis or homogeneous enhancement. Nonenhancement extremely rare. (no image available) Single or multiple mass(es) that are well-circumscribed more commonly than infiltrative mass. Central necrosis, hemorrhage in HIV-positive patients.(no image available) Diffuse growth pattern. Cells surround, infiltrate vessels and perivascular spaces. Several subtypes (large cell accounts for nearly 50%). High nuclear to cytoplasmic ratio (high electron density). MIB-1, proliferation index, usually high (50-70%).(no image available)
         
Neurosarcoid isodense or somewhat hyperdense compared to brain. When parenchymal involvement occurs, there is usually no surrounding edema and, when present, it is minimal (No image available). homogeneously enhance; unlike tuberculous lesions, sarcoid nodules do not develop lucent centers. The non-caseating granulomas of sarcoidosis may be single or multiple. Following steroid treatment CT or MRI may document improvement with decrease in the size and number of lesions, or even their complete disappearance. CECT may show basilar leptomeningeal enhancement (No image available). Granulomatous infiltration of the dura mater causes plaquelike or nodular thickening that may be noted on the infundibular stalk and optic chiasm. The granulomatous lesion is usually isointense to gray matter on T1 (image shows irregular thickening of the optic chiasm, arrow. Note that the leptomeningeal granulomas are not visible on the unenhanced image) usually isointense to hyperintense relative to gray matter on T2-weighted images. Sellar disease may appear cystic (no image available). Distinguish restricted (acute ischemic cytotoxic edema) from nonrestricted neurosarcoid (vasogenic) edema (no image available). Contrast material enhancement is usually homogeneous and better delineates the parenchymal and leptomeningeal involvement (image shows mass elevating the optic chiasm)

(Image shows widespread nodular leptomeningeal and infundibular stalk enhancement, arrows). 		Granulomatous leptomeningitis (most common) or dural-based solitary mass (diffuse > nodular). May infiltrate along perivascular spaces (no image available). Noncaseating granuloma: Compact, radially arranged epithelioid cells with pale-staining nuclei. Large multinucleated giant cells in arc/circle around central granular zone. Arterial wall invasion by epithelioid cell granuloma causing disruption of media and internal elastica. Tissue may then cause luminal stenosis or occlusion. Fibrocollagenous tissue accumulates in dural lesions, correlates with T2 hypointense lesions. Inflammatory infiltration, correlates with T2 hyperintense lesions. (Image shows nonnecrotizing granulomatous inflammation consisting of rounded collections of epithelioid histiocytes surrounded by lymphoid infiltrates, arrows). develops primarily in the leptomeninges and may spread along the Virchow-Robin spaces to form intraparenchymal masses.The disease has a predilection for the base of the brain, particularly the hypothalamus and pituitary gland, although any portion of the CNS may be affected.