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

Medulloblastomas usually form in the fourth ventricle, between the brainstem and the cerebellum. Tumors with similar appearance and characteristics originate in other parts of the brain, but they are not identical to medulloblastoma. ^[1]

Although it is thought that medulloblastomas originate from immature or embryonal cells at their earliest stage of development, the exact cell of origin, or "medulloblast" has yet to be identified.

It is currently thought that medulloblastoma arises from cerebellar "stem cells" that have been prevented from dividing and differentiating into their normal cell types. This accounts from the varying histologic variants seen on biopsy. Rosette formation is highly characteristic of medulloblastoma and is seen in up to half of the cases.

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.

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]

References

↑ Roger Packer M.D, Medulloblastoma Clinical Trials and Noteworthy Treatments for Brain Tumors 2002.
↑ ^2.00 ^2.01 ^2.02 ^2.03 ^2.04 ^2.05 ^2.06 ^2.07 ^2.08 ^2.09 ^2.10 ^2.11 Medulloblastoma. Librepathology(2015) http://librepathology.org/wiki/index.php/Medulloblastoma Accessed on September, 28th 2015

Template:WikiDoc Sources

[1] Roger Packer M.D, Medulloblastoma Clinical Trials and Noteworthy Treatments for Brain Tumors 2002.

[patho-2] 2.00 ^2.01 ^2.02 ^2.03 ^2.04 ^2.05 ^2.06 ^2.07 ^2.08 ^2.09 ^2.10 ^2.11 Medulloblastoma. Librepathology(2015) http://librepathology.org/wiki/index.php/Medulloblastoma Accessed on September, 28th 2015

[1]

[2]