GLIOSARCOMA (ATLAS)

GLIOSARCOMA (WHO Grade IV)

• Gliosarcoma is a malignant glioma that has biphasic tissue pattern wiht alternating areas exhibiting  glial and mesenchymal differentiation

• Stroebe in 1898 introduced the term Gliosarcoma

• It constitutes approximately 2% of all glioblastomas

• Histogenesis – 

  • One theory suggests that sarcomatous component is of vascular origin as the spindle cells demonstrate Factor- VIII related antigens on IHC.

  • Some studies suggest that the sarcomatous portion results from advanced glioma progression with acquisition of sarcomatous phenotype and loss of GFAP expression 

• Genetics – Gliosarcoma have similar genetic aberrations as seen in Glioblastoma. They are 

  • Gain of chromosome 7

  • Loss of chromosome 10 and 17

  • Deletion of short arm of chromosome 9

  • Alterations of chromosome 3

  • Mutations of TP53 tumor suppressor gene and PTEN gene

  • Homozygous P16 (CDKN2A) deletion 

  • Alterations in Rb pathway in some cases

• Age – between 40 and 60 years

• Sex- Males predominance with male to female ratio of 1.8:1

• Localization – Usually cerebrum involving temporal, frontal, parietal and occipital lobes in decreaseing order of frequency

• Clinical features –

  • symptoms depend upon the location of tumor

  • Patient will have short history and presents with seizures and paresis

• Radiological findings –

  • Angiography – shows mixed dural and pial vascular supply

  • CT scan – Features of glioblastoma. If sarcomatous component predominates then tumor appeasr well-demarcated hyperdense mass with homogenous contrast enhancement mimicking meningioma

Gross finding –

• Gliosarcoma are typically firm and well circumscribed in contrast to more infiltrative ill defined glioblastoma

Microscopic findings

• Sarcomatous element is spindle cell proliferation with reticulin, exhibiting either the precise herring bone pattern architecture as in well differentiated fibrosarcoma or fascicles resembling fibrohistiocytoma

• Presence of spindle cells does not justify Glioarcoma. Instead there should be presence of neoplastic mesenchymal component (sarcomatous component) and reticulin formation which separates sarcomatous areas as well demarcated from the glial tumor

• Lines of mesenchymal differentiation other than fibroblastic include –

  • Epithelial

  • Myofibroblastic

  • Cartilage

  • Bone

  • Angiosarcoma

  • Smooth muscle

  • Skeletal muscle

• Gliofibroma – Histogenesis not known 

  • Astrocytic neoplasm occuring in young that shows marked, ubiquitous reticulin positive collagen deposition in matrix around glioma cells

  • In some Gliofibroma, Glioma cells themselves produce collagen (Desmoplastic astrocytoma) where as in others it appears to be deposited by mesenchymal cells (Mixed glioma/fibroma)

Immunohistochemistry

–        Glial component is reactive for GFAP

–        The S-100 and GFAP positivity denotes metaplasia of glial cells to sarcomatous component.

Prognosis –

• Gliosarcoma has better prognosis than glioblastoma but in few studies both had same outcome

References 

• H.Oghgaki, W.Biernat, R.Reis, M.Hegi, P.Kleihues. Gliosarcoma. In: Paul Kleihues and Webster K. Cavence. Pathology and Genetics. Tumors of the Nervous system. WHO Classification of tumors 2000;42-44