Medulloblastoma pathophysiology

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1] Associate Editor(s)-in-Chief: Haytham Allaham, M.D. [2]

Overview

Pathogenesis

Medulloblastoma arises from cerebellar stem cells, which are normally involved in the anatomical development of the cerebellum and other posterior fossa structures.^[1]
Medulloblastoma is usually located at the infratentorial region, where it forms a mass between the brain stem and the cerebellum in the vicinity of the fourth ventricle.^[1]
Medulloblastoma is an invasive and rapidly growing tumor.^[1]
Unlike most brain tumors, medulloblastoma may spread through the cerebrospinal fluid (CSF) and frequently metastasize to different organs of the body.^[1]
Medulloblastoma is often associated with gorlin syndrome and turcot syndrome.^[1]

Genetics

Molecular genetics reveal a loss of genetic information on the distal part of chromosome 17, distal to the p53 gene, possibly accounting for the neoplastic transformation of the undifferentiated cerebellar cells. Medulloblastomas are also seen in Gorlin syndrome as well as Turcot syndrome. Another research has strongly implicated the JC virus, the virus that causes multifocal leukoencephalopathy.

Gross Pathology

Histologically, the tumor is solid, pink-gray in color, and is well circumscribed.

Mircoscopic Pathology

The tumor is very cellular, many mitoses, little cytoplasm, and has the tendency to form clusters and rosettes.

Small round cell tumour, Homer-Wright rosettes: , Rosette with a meshwork of fibers (neuropil) at the centre.

Shown below is a series of microscopic images observed in medulloblastoma:

Medulloblastoma smear^[2]
Medulloblastoma smear ^[2]
Medulloblastoma smear demonstrating Homer-Wright rosettes^[2]
Medulloblastoma smear demonstrating cerebellar infiltrative growth^[2]
Medullloblastoma smear demonstrating demsomplastic nodular growth^[2]
Anaplastic large cell medulloblastoma smear^[2]
Medulloblastoma smear^[2]
Desmoplastic medulloblastoma smear on reticulin stain demonstrating "pale islands"^[2]
Desmoplastic medulloblastoma on MIB-1 immunostaining^[2]
Medulloblastoma smear demonstrating areas of geographic necrosis^[2]
Medulloblastoma smear demonstrating epitheloid ribboning and nuclear moulding of tumor cells^[2]
Medulloblastoma smear demonstrating partial MAP2 immunoreactivity^[2]