Angiocentric astrocytoma in a cat

Abstract

Gliomas are common primary central nervous system neoplasms of dogs and cats, but atypical glioma subtypes are rare. Herein we report an angiocentric astrocytoma in a 15-y-old spayed female domestic shorthaired cat that was euthanized after therapy-resistant seizures. Gross anatomic changes consisted of swelling of the rostral leptomeninges over the olfactory bulbs and rostral telencephalon. Histologically, polygonal-to-elongate atypical neoplastic cells were arranged along perivascular spaces within these areas. Neoplastic cells were positive for glial fibrillary acidic protein, S100 protein, and vimentin. Ultrastructurally, round-to-elongate neoplastic cells emitting long processes with aggregates of intermediary filaments expanded and occupied the spaces between the vascular basement membrane and the glia limitans; nuclei had marginal and central heterochromatin. Tight junctions connected the plasma membrane of neighboring cells. The cell morphology, immunohistochemistry, and ultrastructural findings were consistent with an astrocytoma; the exclusive perivascular arrangement of neoplastic cells with no parenchymal mass warranted the diagnosis of angiocentric astrocytoma.

Keywords: astrocytoma; cats; glioma; immunohistochemistry; neuropathology.

Figures 1–4.

Brain of a cat with angiocentric astrocytoma. Figure 1. The olfactory bulbs are swollen and light-gray to tan with small red areas of hemorrhage (arrow). Figure 2. Cross-section of the formalin-fixed brain showing dark gray areas expanding the cingulate gyri (arrow), septal nuclei (asterisk), and right globus pallidus (arrowhead). Figure 3. Neoplastic cells expand the perivascular spaces within the frontal telencephalon. H&E. Figure 4. Neoplastic cells in a perpendicular arrangement around a blood capillary. H&E.

Figures 5–10.

Brain of a cat with angiocentric astrocytoma. Figure 5. Neoplastic cells have strong immunolabeling for glial fibrillary acidic protein (GFAP). A dense meshwork of normal astrocytic processes delineates the glial limitans and tumor interface. Inset: Closer view of GFAP-positive neoplastic cells. Figure 6. Neoplastic cells have strong immunolabeling for S100 protein. Reactive astrocytes are present around a vascular space expanded by neoplastic cells (arrowhead). Figure 7. Neoplastic cells have strong immunolabeling for vimentin. Figure 8. Transmission electron micrograph of atypical cells (black asterisk) occupying the space between the blood capillary (white asterisk) basement membrane (thin arrow) and pericyte (Pe) and glia limitans (thick arrow). Figure 9. Interface of the glia limitans (arrow) and neoplastic cells (Ne). A reactive astrocyte (As) with abundant cytoplasmic GFAP is also present. Figure 10. Neoplastic cells with polyhedral cytoplasm and a plasma membrane with multiple tight junctions (arrow). The cytoplasm contains bundles of GFAP (asterisks), mitochondria (M), and Golgi complex (arrowhead). The nucleus (N) displays small aggregates of marginal and central heterochromatin.