Traumatic neuromas are an uncommon biopsy submission. They are exuberant, haphazardly growing masses, but are not malignant. They occur following transection of the nerve followed by poor apposition of the two cut ends leading to haphazard growth. In this case, traumatic transection of a nerve by the porcupine quill is considered most likely. In the dog, neuromas are most commonly seen as a consequence of tail docking. Clinically, they are often painful and affected dogs will often be irritated by the mass and scratch at it.
Histopathology April 2017
1: Low magnification with central nerve surrounded by haphazard spindle cells (nerve arrowed).
2 and 3: Higher magnifications characterized by a nerve centrally with increased cellularity (Schwann cell proliferation) surrounded circumferentially by a dense band of variably haphazardly oriented bundles of extracellular matrix of low cellularity with minimal cellular pleomorphism. The cells are predominately delicate spindle cells with scant eosinophilic cytoplasm and often elongate, wavy nuclei.
4: Neurofilament immunohistochemistry: The central, remnant nerve is evident and the axons are variably swollen and thick. There is also disorganized growth.
5: Bielschowsky silver stain: Remnant nerve at the edge of the mass with variably dilated axons.
Subcutaneous mass on the top of the head approximately two years following traumatic encounter with a porcupine. Surgical removal of the mass revealed a white, thick, linear structure on the left side of the face above the zygomatic arch.
Choroid plexus tumors (papilloma or carcinoma) account for 10-20% of all intracranial neoplasms in the dog. These are epithelial neoplasms that arise from the normal choroid plexus and most commonly occur in the lateral ventricles or in the lateral aperture where the choroid plexus is abundant. The designation of papilloma vs. carcinoma is dependent on recognizing spread away from the primary tumor (if spread is noted then carcinoma is designated).
Choroid plexus tumors express a variery of cell adhesion molecules; however, these proteins are not specific to the choroid plexus. Recently, the inward potassium rectifier protein, Kir7.1, has been recognized as a specific immunohistochemical marker for choroid plexus tumors in the dog.
Choi EJ, Sloma EA, Miller AD. Kir7.1 immunoreactivity in canine choroid plexus tumors. J Vet Diag Invest 2016 28(4):464-468.
Reginato A, Girolami D, Menchetti L, Foiani G, Mandara MT. E-cadherin, N-cadherin expression and histologic characterization of canine choroid plexus tumors. Vet Pathol 2016 53(4):788-791.
Histopathology March 2017
1: The mass is composed of arborizing trabeculae and fronds of neoplastic choroid plexus epithelium.
2: Higher magnification of the arborizing trabeculae of neoplastic choroid plexus epithelium. There is very little atypia in this population and no mitoses are noted.
This dog has a large mass that fills part of the lateral ventricle extending into the dorsal third ventricle. The mass distorts and displaces the body of the fornix. The mass is finely granular and is consistent with a choroid plexus tumor.
This dog has a malignant glioma. Gliomas are common in the dog, especially in certain dog breeds (brachycephalic breeds are overrepresented as well as golden retriever). The incidence of intracranial neoplasia in the dog, based on necropsy studies, is approximately 2-5% with gliomas representing approximately 40% of the total number of cases. Histologically, oligodendrogliomas outnumber astrocytomas when large necropsy studies are performed even though some older studies seem to suggest that their numbers are roughly equal. Recent advanced immunohistochemical and molecular studies have confirmed that oligodendrogliomas outnumber the cases of astrocytoma.
The grading scheme for veterinary gliomas is poorly defined and dated and increasing reliance is being given to the human World Health Organization grading system. In this grading system there are four grades of astrocytoma (ranging from lowest grade (grade I; pilocytic astrocytoma) to grade IV (glioblastoma)). Oligodendrogliomas are graded either as a grade II or grade III with the higher grade reserved for cases with glomeruloid blood vessels and serpiginous tracts of necrosis. Although this case lacks glomeruloid vasculature and tracts of necrosis, it has a high mitotic rate and is quite invasive highlighting its aggressive nature. This case is a good example to not overly rely on the human criteria for diagnosing canine gliomas. While there is some overlap, a true veterinary grading scheme is needed.
LeBlanc AK, Mazcko C, Brown DB, Koehler JW, Miller AD, Miller CR, Bentley RT, Packer RA, Breen M, Boudreau B, Levine JM, Simpson MR, Halsey C, Kisseberth W, Rossmeisl Jr, JH, Dickinson PJ, Fan T, Corps K, Aldape K, Puduvalli V, Gilbert MR. Creation of an NCI Comparative Brain Tumor Consortium: Informing the translation of new knowledge from canine to human brain tumor patients. J Neurooncol, 2016, 18(9):1209-1218.
Rissi D, Miller AD. Canine spinal cord glioma: A case series and a review of the literature. J Vet Diag Invest, 2017, 29(1):126-132.
Johnson GC, Coates JR, Wininger F. Diagnostic immunohistochemistry of canine and feline intracalvarial tumors in the age of brain biopsies. Vet Pathol, 2014, 51(1):146-160.
Histopathology February 2017
1: HE, 40x: Sheets of neoplastic round to polygonal cells are interspersed with foci of hemorrhage (correlating to the gross image).
2: HE; 400x: Neoplastic cells vary in morphology with round, to polygonal, to elongate nuclei with finely stippled chromatin. The amount of cytoplasm varies, but for the most part is scant to mild. Atypia is abundant with karyomegaly and multinucleate neoplastic cells. Mitotic figures are common (arrow).
3: HE; 200x: Neoplastic cells spread along the glia limitans and the leptomeninges of the adjacent cortical tissue. This is a common feature of gliomas referred to as secondary structures.
NB: Immunohistochemistry for Olig2 confirmed the glial origin of the neoplastic cells; however, other IHC markers (GFAP, CNPase) failed to further define the lineage of the cells and therefore this was diagnosed as a poorly differentiated glioma.
Brain removed and submitted for histopathology. Within the region of the left caudate nucleus extending caudally to involve the thalamus is an expansile, tan to white mass that is speckled with foci of hemorrhage. The left lateral ventricle is obscured by the neoplasm and there is a moderate midline shift. The gross findings are most consistent with a glioma.