Neurofibroma (NF): NFs are diffusely infiltrating, extraneural

tumors that consist of Schwann cells and fibroblasts. Solitary

scalp NFs occur. Multiple NFs or plexiform NFs occur as part of

NF1. NFs correspond histologically to WHO grade I. Plexiform

NFs may degenerate into malignant peripheral nerve sheath

tumors (MPNSTs). MPNSTs are graded from WHO II to IV, an

approach similar to sarcoma grading.

Lymphomas and Hematopoietic Tumors

Primary CNS Lymphoma (PCNSL): As a result of HAART

therapy in HIV/AIDS patients, as well as in other

immunocompromised individuals, PCNSLs are dramatically

increasing in prevalence. PCNSL can occur as both focal

parenchymal and intravascular tumor. PCNSL can be single or

multiple and is most commonly seen in the cerebral

hemispheres. More than 95% of PCNSLs are diffuse large Bcell lymphomas.

Germ Cell Tumors

Intracranial germ cell tumors are morphologic homologues of

germinal neoplasms that arise in the gonads and extragonadal

sites. 80-90% occur in adolescents. Most occur in the midline

(pineal region, around the 3rd ventricle).

Sellar Region Tumors

Craniopharyngioma: Craniopharyngioma is a benign (WHO

grade I), often partially cystic neoplasm that is the most

common nonneuroepithelial intracranial neoplasm in children.

It shows a distinct bimodal age distribution, with the cystic

adamantinomatous type seen mostly in children and a 2nd,

smaller peak in middle-aged adults. The less common papillary

type is usually solid and found almost exclusively in adults.

Miscellaneous sellar region tumors: Granular cell tumor of

the neurohypophysis is a rare tumor of adults that usually

arises from the infundibulum. Pituicytomas are glial

neoplasms of adults that also usually arise within the

infundibulum. Spindle cell oncocytoma of the

adenohypophysis is a nonendocrine neoplasm of the

adenohypophysis. These rare tumors are all WHO grade I.

Brain: Pathology-Based Diagnoses: Neoplasms,

Cysts, and Disorders

126

Neoplasms Overview

Neuroepithelial Tumors

Neoplasm Grade Neoplasm Grade Neoplasm Grade

Astrocytic Choroid plexus Neuronal, mixed neuronal-glial

Pilocytic astrocytoma I Choroid plexus papilloma I Gangliocytoma I

Pilomyxoid astrocytoma II Atypical choroid plexus papilloma II Ganglioglioma I

Subependymal giant cell astrocytoma I Choroid plexus carcinoma III DIG/DIA I

Pleomorphic xanthoastrocytoma II DNET I

Anaplastic astrocytoma III Pineal region Central neurocytoma II

Glioblastoma IV Pineocytoma I Extraventricular neurocytoma II

Gliosarcoma IV PPTID II-III Cerebellar liponeurocytoma II

Gliomatosis cerebri III, II-IV Pineoblastoma IV Paraganglioma (spinal cord) I

Papillary tumor of pineal region II-III Papillary glioneuronal tumor I

Oligodendroglial Rosette-forming glioneuronal

tumor

I

Oligodendroglioma II Ependymal

Anaplastic oligodendroglioma III Subependymoma I Other neuroepithelial

Oligoastrocytoma Variable Myxopapillary ependymoma I Astroblastoma

Ependymoma II Chordoid glioma of 3rd ventricle II

Embryonal Anaplastic ependymoma III Angiocentric glioma (angiocentric

neuroepithelial tumor)

I

Medulloblastoma IV

Primitive neuroectodermal tumor IV

Atypical teratoid-rhabdoid tumor IV

Meningeal Tumors

Neoplasm Grade Neoplasm Grade Neoplasm Grade

Meningothelial Nonmeningothelial mesenchymal Primary melanocytic

Meningioma I Lipoma I Diffuse melanocytoma

Atypical meningioma II Liposarcoma Melanocytoma

Anaplastic/malignant meningioma III Chondroma I Malignant melanoma

Chondrosarcoma Meningeal melanomatosis

Other related Osteoma

Hemangioblastoma I Osteosarcoma

Osteochondroma

Hemangioma I

Hemangiopericytoma II-III

Other Tumors

Neoplasm Grade Neoplasm Grade Neoplasm Grade

Cranial and spinal nerve tumors Germ cell tumors Sellar region tumors

Schwannoma I Germinoma Craniopharyngioma I

Neurofibroma I Embryonal carcinoma Adamantinomatous

MPNST II-IV Yolk sac tumor Papillary

Mixed germ cell tumor Granular cell tumor of

neurohypophysis

I