Cytology and histology of a high-grade oligodendroglioma with embryonal features in a dog

A 10-y-old castrated male German Wirehaired Pointer dog was presented for referral evaluation of a brain mass and craniotomy. Pertinent history included acute onset of cluster seizures; the systemic physical examination was largely unremarkable. Thorough laboratory and imaging screening ruled out extracranial causes for the presenting clinical signs. MRI revealed a hemorrhagic and strongly contrast-enhancing mass in the left frontal lobe. Upon craniotomy, the lesion was abnormal cortical parenchyma with surrounding malacic tissue, which was excised and submitted for microscopic analyses. Cytologic examination of a squash preparation of the mass revealed a mildly inflamed and hemorrhagic neoplasm, with oligodendroglioma or an embryonal CNS neoplasm as primary differential diagnoses. Histopathology with immunohistochemistry confirmed a high-grade oligodendroglioma with embryonal morphology.