Diagnostic immunohistochemistry of primary and secondary central nervous system neoplasms of dogs and cats

Abstract

The diagnosis of primary and secondary CNS neoplasms of dogs and cats relies on histologic examination of autopsy or biopsy samples. In addition, many neoplasms must be further characterized by immunohistochemistry (IHC) for a more refined diagnosis in specific cases. Given the many investigations assessing the diagnostic and prognostic IHC profile of CNS neoplasms in the veterinary literature, it may be difficult for the diagnostic pathologist or pathology trainee to narrow the list of reliable diagnostic IHCs when facing a challenging case. Here we compile a comprehensive list of the most diagnostically relevant immunomarkers that should be utilized for the diagnostic support or confirmation of the most common primary and secondary CNS neoplasms of dogs and cats.

Keywords: CNS tumors; cats; dogs; glioma; immunohistochemistry, meningioma; neuropathology.

Figures 1–3.

Meningioma in the brain of a cat. Figure 1. Meningothelial meningioma characterized by sheets and lobules of neoplastic meningothelial cells with abundant eosinophilic cytoplasm and round-to-oval nuclei. H&E. Figure 2. Neoplastic meningothelial cells with widespread membranous immunolabeling for vimentin. Figure 3. Neoplastic meningothelial cells with widespread membranous immunolabeling for E-cadherin.

Figures 4–8.

Oligodendroglioma in the brain of a dog. Figure 4. Low-grade oligodendroglioma characterized by sheets of neoplastic cells and a mucinous and fine capillary stroma. H&E. Figure 5. High-grade oligodendroglioma characterized by dense sheets of neoplastic cells and a fine capillary stroma. H&E. Figure 6. Neoplastic cells with widespread nuclear immunolabeling for OLIG2. Figure 7. Reactive astrocytes among neoplastic cells have cytoplasmic immunolabeling for GFAP. Figure 8. Neoplastic cells with widespread cytoplasmic immunolabeling for CNPase.

Figures 9–10.

Astrocytoma in the brain of a dog. Figure 9. Low-grade astrocytoma characterized by scattered elongate neoplastic cells and a fibrillary, neuroparenchyma-like stroma. H&E. Figure 10. Neoplastic cells with widespread cytoplasmic immunolabeling for GFAP.

Figures 11–16.

Astrocytoma in the brain of a dog. Figure 11. High-grade astrocytoma characterized by bundles of neoplastic cells and a neuroparenchyma-like stroma. H&E. Figure 12. Robust cytoplasmic immunolabeling for GFAP throughout the astrocytic cell bodies and processes. Figure 13. Robust cytoplasmic immunolabeling for GFAP is more prominent in the astrocytic cell bodies. Figure 14. Robust cytoplasmic immunolabeling for GFAP is more prominent in the astrocytic cell processes, with only rare cell bodies labeled (arrow). Figure 15. Neoplastic cells with patchy nuclear immunolabeling for OLIG2. Figure 16. Neoplastic cells (particularly cell processes) with widespread cytoplasmic immunolabeling for MAP2.

Figures 17–20.

Ependymoma in the brain of a cat. Figure 17. Classic ependymoma characterized by neoplastic cells surrounding a blood vessel (pseudorosette) supported by a fine fibrovascular stroma. H&E. Figure 18. Patchy cytoplasmic immunolabeling for GFAP predominantly within neoplastic cells forming pseudorosettes. Figure 19. Neoplastic cells with patchy cytoplasmic immunolabeling for CKAE1/3, predominantly in cells forming pseudorosettes. Figure 20. Neoplastic cells with widespread nuclear immunolabeling for OLIG2.

Figures 21–24.

Choroid plexus tumor in the brain of a dog. Figure 21. Choroid plexus papilloma characterized by neoplastic cells forming papillary projections supported by a stalk of fibrovascular stroma. H&E. Figure 22. Neoplastic cells with widespread cytoplasmic immunolabeling for CKAE1/3. Figure 23. Neoplastic cells with widespread cytoplasmic immunolabeling for E-cadherin. Figure 24. A cluster of neoplastic cells with cytoplasmic immunolabeling for GFAP.

Figures 25–28.

Ganglioglioma in the spinal cord of a dog. Figure 25. Neoplastic neurons (arrows) are interspersed with neoplastic glial cells (arrowhead) throughout. Figure 26. Neoplastic neurons with moderate cytoplasmic immunolabeling for NeuN. Figure 27. Neoplastic glial cells with robust nuclear immunolabeling for OLIG2. Figure 28. Neoplastic glial cells with robust cytoplasmic immunolabeling for GFAP.

Figures 29–34.

Embryonal and germ cell neoplasms in the brains of dogs. Figure 29. Embryonal neoplasm characterized by sheets of neoplastic round cells. Figure 30. Neoplastic embryonal cells with cytoplasmic immunolabeling for MAP2. Figure 31. Neoplastic embryonal cells with cytoplasmic immunolabeling for SYN. Figure 32. Scattered neoplastic embryonal cells with nuclear immunolabeling for OLIG2. Figure 33. Suprasellar germ cell tumor consisting of sheets of round germ cells (left) and hepatocyte-like cells with cytoplasmic lipid vacuoles and occasional acinar structures (inset). Figure 34. Neoplastic cells in a suprasellar germ cell tumor have robust cytoplasmic immunolabeling for α-fetoprotein.

Figures 35, 36.

Ectopic nephroblastoma in the spinal cord of a dog. Figure 35. The neoplasm consists of an epithelial component forming tubules (arrowhead) and primitive glomeruli (arrow), and a mesenchymal component (asterisk). Figure 36. Neoplastic cells with nuclear immunolabeling for WT1.

Figures 37–42.

Round cell neoplasms in the brains of cats. Figure 37. Encephalic lymphoma characterized by sheets of neoplastic lymphocytes supported by a fine fibrovascular stroma. H&E. Figure 38. Encephalic T-cell lymphoma with widespread membranous immunolabeling for CD3. Figure 39. Encephalic B-cell lymphoma with widespread membranous immunolabeling for CD79. Figure 40. Encephalic histiocytic sarcoma characterized by sheets of neoplastic histiocytes supported by a fine fibrovascular stroma. H&E. Figure 41. Encephalic histiocytic sarcoma with widespread cytoplasmic immunolabeling for Iba1. Figure 42. Encephalic histiocytic sarcoma with widespread cytoplasmic immunolabeling for CD204.