Neuropath - Tumors and Cysts

• Medulloblastoma aka infratentorial PNET
• Tumor common in children arising from the roof of the 4th ventricle
• Densely packed, dark blue cells + Synaptophysin (marker neuronal diff.) and + Reticulin
• Homer-Right Rosettes in ~40% (attempts at neuroblastic differentiation) lacking a vascular core
• Early CSF metastesis and leptomeingeal mets

• HomerWright Rosettes as seen in a Meduloblastoma
• Attempts at neuroblastic differentiation lacking a vascular core

Retinoblastoma

True rosettes of Flexner-Wintersteiner

• Gross Juvenile Pilocytic Astrocytoma
• Unencapsulated but well-circumscribed,heterogenous in appearance with both cystic and nodular components
• Propensity for the 4th ventricle in children

• Juvenile Pilocytic Astrocytoma
• Well-circumscribed, cystic lesion with a mural nodule in the CBLM or BS

• Juvenile Pilocytic Astrocytoma
• Characteristic bipolar cells with long, thin hair-like processes- Alternates between densely and loosely lacked regions and microcystic spaces
• Rosenthal Fibers (thick, elongated, red cigar / corkscrew-shaped eosinophilic bodies, the product of long-standing glial tumors made by astrocytic processes)

Low-grade astrocytoma

• Lowgrade Astrocytoma
• Mostly hemispheric (temporal and frontallocations), no contrast enhancement

• Low-grade Astrocytoma
• Infiltrative with ill-defined borders, Increased Cellularity, “bland nuclei”, no mitotic figures

GBM

• GBM
• Increased Cellularity with mitotic profiles and angiogenesis
• Psedopallisading array arranged around regions of central necrosis
• May show glomeruloid hyperplasia

• GBM
• Deep GM / WM (Thal +BG) 
• + Ring Enhancement

• Pleomorphic Xanthoastrocytoma (PEXA)
• Supratentorial (50% T), Contrast enhancing ring, cystic c/a mural nodule

• Pleomorphic Xanthoastrocytoma
• Large, foamy cells with eosinophilic cytoplasm,and  lipids,Nuclear pleomorphism with rare mitoses
• Generally look worse histologically than one would expect
• Often have EGBs

• Subependymal Giant Cell Astrocytoma (SEGA) as seen in Tuberous Sclerosis
• Most commonly at the IVF of Monro

• Oligodendroglioma
• Often involve cortex (Frontal > Temporal) with hemorrhage and Calcifications

• “Fried Egg” appearance due to artificial clearing of cytoplasm
• “Chicken Wire” → calcified blood vessels between cells
• 70% will be associated with a 1p19q co-deletion

CNS Lymphoma with typical perivascular leukocytic infiltrates

• CNS Lymphoma
• Normally in the Frontal lobes and Deep WM withIsointense T2 and ring enhancement; Often multifocal

• Ependymoma
• Tumor of the fourth ventricle eminating from the roof with apparent vascularization

• Ependymoma
• Small, dark, round-oval nuclei with a dense vascular background interrupted by acellular regions called Pseudorosettes (cells surrounding a normal blood vessel)

• Choroid Plexus Papilloma
• +Transthyretin

Pituitary Adenoma

• Craniopharyngioma
• Tumor of the sellar / hypothalamic region with solid and cystic components.

• Craniopharyngioma
• Solid and cystic components
• Islands of columnar cells in a collagen matrix
• Nodules of plump Ketatin

• Meningioma
• 2nd most common (20%), ♀ 2x > ♂, 5th– 7th decade 90% asymp

• Meningioma
• 90% Supratentorial
• Often Parasagital
• + Enhancement
• Dural Tag

• Schwannoma
• Benign, Increased in NF-2, F > M, Peak 4th – 5th , Decreased hearingVertigo, Tinitis

Antoni A (spindles in compact fascicles) and Antoni B (spindles in myxomatous, microcystic array)