OLIGODENDROGLIOMA

OLIGODENDROGLIOMA

• It is an infiltrating glial tumor composed of cells resembling oligodendrocytes.

• Site – Occurs through out the neuraxis but primarily affects cerebral cortex

• Age – Usually in adults (rarely in children)

• Clinical presentation – patient presents with seizures in most cases where lesion is in cerebral cortex. Large lesions present with signs and symptoms of increased intracranial pressure

• Gross finding – infiltrating gliomas are gray white where as highly cellular grade III tumors are fleshy masses, but with out central areas of necrosis as seen in Glioblastoma

• Microscopic findings

  • Histologic and cytologic monotony

  • Low magnification – uniform blueness to section

  • Tumour cells have round nuclei with small prominent nucleoli and with open and bland chromatin

  • Perinuclear halos produce “fried egg” artefact. oligodendrocytes are susceptible to autolytic water imbibition resulting in clear perinuclear halo. These halos are absent in frozen section or specimen fixed promptly

  • Palisading or tightly cohesive clusters of cells  (may be seen in Grade III lesion)

  • Circumscribed nodules of increased cellularity in the background of low grade tumor may occur.

  • Minigemistocytes and gliofibrillary oilgodendrocytes can occur. MInigemistocytes resmble miniature, process containing gemistocytes. Gliofibrillary oligodendrocytes have cytoplasm filled with brightly eosinophilic fibrils that form cap like paranuclear tufts or perinuclear bands. These GFAP positive cells are seen mostly in perivascular regions

  • Rich branching capillaries are noted (chicken wire like)

  • Less specific findings-

    • microcalcifications

    • mucin rich microcystic spaces

    • perineuronal satellitosis

    • perivascular aggregation

    • subpial condensation

  • In grade III lesions fibrillated epithelioid cells containing refractile eosinophilic bodies resembling minute Rosenthal fibres are seen. some cells show filamentous whorls in cytoplasm

  • Spindle cell change is also seen in grade III lesions

• Grade II tumors

  • Pauci cellular

  • Minimal cytologic atypia

  • Blood vessels increased in number but are delicate

• Grade III tumors (Anaplastic oligodendroglioma)

  • Cellular tumors

  • Nuclear hyperchromasia is present

  • Brisk mitotic activity (>6 mitotic figures/10 HPF)

  • Microvascular proliferation (intraluminal endothelial cell proliferation)

  • Necrosis may be present but perinecrotic pseudopalisading is usually absent

  • Eosinophilic “astrocyte like cytoplasm, either with prominent processes that resemble astrocytoma or spindle cell change is seen in grade III neoplasm

  • Well circumscribed epithelioid like appearance

  • Minigemistocytes are common in grade III

• Immunohistochemistry

  • Tumor cells are positive for

    • Olig 2

    • GFAP

    • Neu N

    • Synaptophysin – few cases

  • MIB -1 index greater than 3% has low survival rate

• Differential diagnosis 

  • Diffuse astrocytoma –

    • Cells have cigar shaped nuclei with cytoplasm of varying amount

    • Cells are present in fibrillary background which is absent in Oligopdendroglioma

    • Calcification are rare in Diffuse astrocytoma and lack chicken wire like vasculature

  • Clear cell ependymoma 

    • IHC – shows dot like intracytoplasmic EMA staining

    • Histologically prominent perivascular pseudorosette of surrounding brain and nuclear groove

  • Dysembryoplastic neuroepithelial tumor (DNT)

    • Nodular architecture

    • Loose textured specific glioneuronal element

    • Neurons in DNT float in mucoid background

    • Perineuronal satellitosis is absent 

    • Special stain – Alcian blue  positive 

  • Neurocytic neoplasms

    • Both central and extraventricular neurocytomas resemble oligodendroglioma as they have striking uniformity and rounded nuclei. perinuclear halo and calcifications can also occur

    • IHC – Cells are positive for Synaptophysin

  • Metastatic carcinoma – can be differentiated by IHC 

Reference 

Peter C. Burger, Bernd W. Scheithauer. Tumors of the Neuroglia and Choroid plexus. In: Tumors of the Central Nervous system. AFIP Atlas of tumor pathology. Series 4. Chapter 3. 122-143.