Primitive Neuroectodermal Tumors of the Central Nervous System 

  • Author: Subrata Ghosh, MD, MBBS; Chief Editor: Tarakad S Ramachandran, MBBS, FRCP(C), FACP   more...
 
Updated: Aug 29, 2011
 

Background

Primitive neuroectodermal tumors (PNET) are neoplasms of which medulloblastoma is the prototype. These are small cell, malignant embryonal tumors showing divergent differentiation of variable degree along neuronal, glial, or rarely mesenchymal lines. Only tumors of the CNS are discussed here. Peripheral primitive neuroectodermal tumors are regarded as distinct entities.[1]

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Pathophysiology

PNET of the CNS can be divided grossly into infratentorial tumors (medulloblastoma or iPNET) and supratentorial tumors (sPNET).

Considerable controversy exists regarding the histogenesis of these tumors. Initially, these dense, cellular, embryonal tumors were thought to have a common origin from primitive neuroectodermal cells and to differ only in their location, type, and degree of differentiation. In the revised World Health Organization (WHO) classification, however, many of these tumors are given a separate niche on the basis of the assumption that these embryonal tumors also could arise from cells already committed to differentiation.[2]

Regardless of the controversy, these tumors are discussed as infratentorial (medulloblastoma) and supratentorial. The latter occur rarely (25:1) and are more common in young adults than infratentorial tumors.

Spinal dissemination via the cerebrospinal fluid (CSF) is the most common form of metastatic spread of PNETs.

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Epidemiology

Frequency

United States

Medulloblastoma represents the most common type of primary solid malignant brain tumor in children (as many as 30% of all solid brain tumors). In contrast, only 1% of brain tumors in adults are medulloblastomas. The overall annual incidence is approximately 0.5 case per 100,000 children. Seventy-five percent arise in the midline (vermis), while 25% occur in the lateral cerebellum.

International

The Swedish Cancer Registry reported, as part of a population-based study, that medulloblastomas represented 21% of all primary brain tumors in children. Similar figures were provided by the British Tumor Registry and from the United States (Surveillance, Epidemiology and End Results Program).

Mortality/Morbidity

Risk of sudden death secondary to obstructive hydrocephalus has been hypothesized; however, it is not often observed clinically.

Race

National Cancer Survey suggests a slightly higher incidence in white than in blacks.

Sex

A slight male preponderance is observed (male-to-female ratio 1.8:1).

Age

Three fourths of these tumors appear in children younger than 15 years, and 50% are seen in the first decade of life. A second, smaller peak occurs in young adults (aged 21-40 y).[1] Cerebellar medullobastoma occurs rarely in the elderly.[3]

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Contributor Information and Disclosures
Author

Subrata Ghosh, MD, MBBS  Staff Physician, Division of Neurosurgery, St. Luke's Episcopal Hospital, Texas Medical Center, Houston; Assistant Professor of Neurosurgery, Baylor College of Medicine

Subrata Ghosh, MD, MBBS is a member of the following medical societies: American Association of Neurological Surgeons, American Medical Association, Congress of Neurological Surgeons, and Texas Medical Association

Disclosure: Nothing to disclose.

Coauthor(s)

Draga Jichici, MD, FRCP, FAHA  Associate Clinical Professor, Department of Neurology and Critical Care Medicine, McMaster University School of Medicine, Canada

Draga Jichici, MD, FRCP, FAHA is a member of the following medical societies: American Academy of Neurology, Canadian Congress of Neurological Sciences, Canadian Congress of Neurological Sciences, Canadian Congress of Neurological Sciences, Canadian Critical Care Society, Canadian Medical Protective Association, Canadian Neurocritical Care Society, Neurocritical Care Society, Royal College of Physicians and Surgeons of Canada, and Society of Critical Care Medicine (USA)

Disclosure: Nothing to disclose.

Specialty Editor Board

Roberta J Seidman, MD  Associate Professor of Clinical Pathology, Stony Brook University; Director of Neuropathology, Department of Pathology, Stony Brook University Medical Center

Roberta J Seidman, MD is a member of the following medical societies: American Academy of Neurology, American Association of Neuropathologists, New York Association of Neuropathologists (The Neuroplex), and Suffolk County Society of Pathologists

Disclosure: Nothing to disclose.

Francisco Talavera, PharmD, PhD  Adjunct Assistant Professor, University of Nebraska Medical Center College of Pharmacy; Editor-in-Chief, Medscape Drug Reference

Disclosure: Medscape Salary Employment

Jorge C Kattah, MD  Head, Associate Program Director, Professor, Department of Neurology, University of Illinois College of Medicine at Peoria

Jorge C Kattah, MD is a member of the following medical societies: American Academy of Neurology, American Neurological Association, and New York Academy of Sciences

Disclosure: Biogen Honoraria Consulting; Bayer Corporation Honoraria Consulting

Chief Editor

Tarakad S Ramachandran, MBBS, FRCP(C), FACP  Professor of Neurology, Clinical Professor of Medicine, Clinical Professor of Family Medicine, Clinical Professor of Neurosurgery, State University of New York Upstate Medical University; Chair, Department of Neurology, Crouse Irving Memorial Hospital

Tarakad S Ramachandran, MBBS, FRCP(C), FACP is a member of the following medical societies: American Academy of Neurology, American Academy of Pain Medicine, American College of Forensic Examiners, American College of International Physicians, American College of Managed Care Medicine, American College of Physicians, American Heart Association, American Stroke Association, Royal College of Physicians, Royal College of Physicians and Surgeons of Canada, Royal College of Surgeons of England, and Royal Society of Medicine

Disclosure: Abbott Labs None None; Teva Marion None None; Boeringer-Ingelheim Honoraria Speaking and teaching

References

  1. Mueller S, Chang S. Pediatric brain tumors: current treatment strategies and future therapeutic approaches. Neurotherapeutics. Jul 2009;6(3):570-86. [Medline].

  2. Kleihues P, Burger PC, Scheithauer BW. The new WHO classification of brain tumours. Brain Pathol. Jul 1993;3(3):255-68. [Medline].

  3. Huppmann AR, Orenstein JM, Jones RV. Cerebellar medulloblastoma in the elderly. Ann Diagn Pathol. Feb 2009;13(1):55-9. [Medline].

  4. Gulino A, Arcella A, Giangaspero F. Pathological and molecular heterogeneity of medulloblastoma. Current Opinions in Oncology. November 2008;20(6):668-75.

  5. Guessous F, Li Y, Abounader R. Signalling pathways in Medulloblastoma. Journal of Cell Physiology. December 2008;217(3):577-583.

  6. Roussel MF, Robinson G. Medulloblastoma: advances and challenges. F1000 Biol Rep. 2011;3:5. [Medline]. [Full Text].

  7. Crawford JR, Rood BR, Rossi CT, Vezina G. Medulloblastoma associated with novel PTCH mutation as primary manifestation of Gorlin syndrome. Neurology. May 5 2009;72(18):1618. [Medline].

  8. Allen JC, Donahue B, DaRosso R, Nirenberg A. Hyperfractionated craniospinal radiotherapy and adjuvant chemotherapy for children with newly diagnosed medulloblastoma and other primitive neuroectodermal tumors. Int J Radiat Oncol Biol Phys. Dec 1 1996;36(5):1155-61. [Medline].

  9. Albright AL, Pollack IF, Adelson PD. Principles and Practice of Pediatric Neurosurgery. 1st ed. New York: Thieme;1999: 591-608.

  10. Goldwein JW, Radcliffe J, Johnson J, et al. Updated results of a pilot study of low dose craniospinal irradiation plus chemotherapy for children under five with cerebellar primitive neuroectodermal tumors (medulloblastoma). Int J Radiat Oncol Biol Phys. Mar 1 1996;34(4):899-904. [Medline].

  11. Graham DI, Lantos PL. Greenfield's Neuropathology. Vol 2. 6th ed. New York: Oxford University Press; 1997:698-710.

  12. Kay A, et al. Brain tumors. First ed. New York: Churchill Livingstone; 1997:561-574.

  13. Kleihues P, Cavanee WK. Pathology and genetics of tumours of the nervous system. Lyon, France: International Agency for Research on Cancer (IARC); 1997:49-55.

  14. Kun LE. Brain tumors. Challenges and directions. Pediatr Clin North Am. Aug 1997;44(4):907-17. [Medline].

  15. Prados MD, Wara W, Edwards MS, et al. Treatment of high-risk medulloblastoma and other primitive neuroectodermal tumors with reduced dose craniospinal radiation therapy and multi-agent nitrosourea-based chemotherapy. Pediatr Neurosurg. Oct 1996;25(4):174-81. [Medline].

  16. Rood BR, Macdonald TJ, Packer RJ. Current treatment of medulloblastoma: recent advances and future challenges. Semin Oncol. Oct 2004;31(5):666-75. [Medline].

  17. Russell DS, et al. Pathology of Tumors of the Nervous System. 4th ed. Baltimore: Williams & Wilkins; 1977:203-26.

 
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Cerebellar medulloblastoma. This MRI (axial view, T2-weighted image) demonstrates the heterogeneity of the tumor.
Cerebellar medulloblastoma. This sagittal view MRI without contrast demonstrates characteristic midline cerebellar location with mild obstructive hydrocephalus.
Cerebellar medulloblastoma. This axial view CT scan with contrast shows a partially enhancing mass arising in the midline from cerebellum and filling the fourth ventricle.
 
 
 
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