Oligodendroglioma

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Fig. 1. MRI of cat at the level of the cerebellum and fourth ventricle; T1-weighted image. Note the separate contrast-enhancing masses within the fourth ventricle (wide arrow) and in the basilar meninges (thin arrows). Bar = 1 cm. Fig. 2. CSF cytospin preparation of a cat. Note the large presumptive tumor cells with large, round, dense slightly eccentric nuclei and densely staining bluish cytoplasm with ruffled cytoplasmic borders (arrow). Other cells are macrophages. Wright's stain. Bar = 16 µm. Fig. 3. Fixed brain of a cat. Compare this transverse section to that in Fig. 1, with the intraventricular localization of the oligodendroglioma (wide arrow) and prominent growth in the basilar meninges (thin arrows). Bar = 33 mm.

Fig. 4. Anaplastic oligodendroglioma, brain; cat No. 1. There are several foci of acute necrosis with central mineralization. Note the sheets of round to ovoid nuclei with prominent eosinophilic cytoplasm. HE. Bar = 70 µm. Fig. 5. Anaplastic oligodendroglioma, brain of cat. Fig. 5a. Note the line of prominent glomeruloid vascular proliferation. HE. Bar = 80 µm. Fig. 5b. Immunocytochemical localization of human von Willebrand factor VIII antigen in the glomeruloid vascular proliferation in cat No. 1. Streptavidin–biotin stain. Bar = 50 µm.

Fig. 6. Oligodendroglioma, brain of cat. Extension of the tumor into the basilar subarachnoid space. Note the entrapment of the nerve root, which is morphologically intact. HE. Bar = 60 µm. Fig. 7. Oligodendroglioma, brain of cat. Fig. 7a. Numerous reactive astrocytes are present throughout the tumor. Streptavidin–biotin for GFAP. Bar = 40 µm. Fig. 7b. Numerous GFAP-positive, GFOC-like cells. Note the cytoplasmic staining pattern with the thin round rim of perinuclear localization of GFAP and with minimal processes. Streptavidin biotin for GFAP. Bar = 40 µm.

Oligodendrogliomas are reported as the third most common primary brain tumour in cats^[1].

These tumours arise from a glioma which arise from oligodendrocytes, the myelin-producing cells of the central nervous system. These tumours appear to affect the supratentorial and infratentorial compartments of the brain equally^[2]. MRI characteristics of these tumours display heterogenous contrast enhancement and hyperintensity on PW and T2-weighted images and either iso- or hypointensity on the T1-weighted images.

Clinical signs

Oligodendrogliomas are more common in older cats (usually >10 years) with a progressive history of neurological signs. Clinical signs are often nonspecific and include vestibular disorders, behaviour changes, locomotor deficits (circling, pacing), lethargy, anorexia, and vomiting. Seizures are a common presenting sign in one quarter of cases^[3]. There appears to be no breed or sex predilection with this disease^[4].

Diagnosis

Diagnosis of this tumour type depends primarily on histological diagnosis. CSF analysis is nonspecific, but most often shows mild to moderate increases in total protein and nucleated cell counts^[5].

The histologic diagnosis of oligodendroglioma tends to be relatively simple in animals, but human oligodendrogliomas share some gross (intraventricular growth) and histologic (calcification and perinuclear halos) similarities to the recently defined central neurocytoma of neuronal origin^[6]. However, in these feline cases, both the cytological features (vascular proliferation, myxoid-like cysts, and calcification) and the negative staining for neuron-specific antigens would help to exclude this diagnosis. The minimal CD45R staining in both tumors also rules out the more unlikely possibility of a lymphoma^[7].

Treatment

Surgical excision is the therapy of choice, however, difficulty in complete removal of oligodendrogliomas can be difficult. Prognosis is good, but adjunct radiation therapy will improve survival rates as with most brain tumours.

Chemotherapy and conservative treatment tends to reduce survival rates in feline oligodendrogliomas.

References

1. ↑ Troxel, MT (2010) Brain tumours: clinical spectrum. In August, JR (Ed): Consultations in feline internal medicine. Vol 6. Elsevier Saunders, Philadelphia. pp:548
2. ↑ LeCouteur RA, et al (1983) X-ray computed tomography of brain tumors in cats. J Am Vet Med Assoc 183:301-305
3. ↑ Tomek, A et al (2006) Intracranial neoplasia in 61 cats: localisation, tumour types and seizure patterns. JFMS 8:243
4. ↑ Troxel, MT et al (2003) Feline intracranial neoplasia: retrospective review of 160 cases (1985-2001). J Vet Intern Med 17:850
5. ↑ Dickinson, PJ et al (2000) Clinical and pathological features of oligodendrogliomas in two cats. Vet Pathol 37:160
6. ↑ Small E (1964) Diseases of the central nervous system. In: Feline Medicine and Surgery, ed. Catcott EJ, 1st ed., pp 303-314, American Veterinary Publications, Santa Barbara, CA 1964
7. ↑ Smith DA, Honhold N (1988) Clinical and pathological features of a cerebellar oligodendroglioma in a cat. J Small Anim Pract 29:269-274