Case 170519-3

Seven-year-old male castrated French bulldog

There was no significant previous medical history. The patient was presented for acute onset of a progressive non-ambulatory paraplegia of 3 days’ duration. At physical examination he was painful upon thoracolumbar palpation, and had absent pelvic limb reflexes bilaterally. MRI findings indicated intradural hemorrhage in the spinal cord in the region of T2-T4, with no identified etiology. The patient was euthanized due to poor prognosis and submitted for necropsy.

The thoracic spinal cord from the level of T1 T4 had patchy, dark red-purple foci. Moderate subdural hemorrhage was present in the lumbar spinal cord (L2 to L5), and transection of the cord (post-fixation) demonstrated a large, central, blood-filled cavitation extending from approximately T1 to T4. Hemorrhage exuded from the central canal upon transection of the cord as far back as L3. Intervertebral discs were mineralized between C2 and C7, and in the lumbar vertebral column between L6 and L7. A flat plate of mineralization was in the dura overlying the L6 vertebra. The T9 vertebral body was trapezoidal with a narrowed ventral aspect when viewed in sagittal section. The T13 vertebral body was wedge-shaped with a longitudinally narrowed ventral aspect, with resultant angulation of the vertebral column (kyphosis). Other gross lesions were clinically irrelevant.

This transverse section of spinal cord has a proliferative cell population admixed with effacing hemorrhage and necrosis, regionally and asymmetrically affecting approximately 60% of the cord. The proliferative cell population is characterized by a delicate network of round cells with small, densely basophilic nuclei surrounded frequently by clear space, which creates an overall honeycomb-like appearance. These cells are supported by a fine, fibrovascular network with thin, branching vasculature. Anisocytosis and anisokaryosis are mild with rare mitotic figures (approximately one per ten high power fields) and occasional single cell necrosis. Infiltrating cells form a band lining approximately 30% of the dura as well as tracking along the leptomeninges, occasionally surrounding associated nerve roots. There is moderate meningothelial hyperplasia in these regions. Within the region of necrosis are moderate numbers of neutrophils, lymphocytes, and plasma cells, with fewer macrophages. Remnant spinal cord parenchyma is moderately gliotic with multifocal small foci of hemorrhage, myelin sheath swelling, occasional digestion chambers and multifocal neuronal necrosis.

The neoplastic cells are variably immunoreactive with Olig2, most prominently peripherally. Some central cells exhibit strong, positive, cytoplasmic immunoreactivity (fully differentiated oligodendrocytes). The neoplasm was not immunoreactive with glial fibrillary acidic protein (GFAP).

A trichrome stain demonstrated minimal fibrosis associated with the dural margins and proliferative meningothelial tissue.

Spinal cord: oligodendroglioma with marked hemorrhage, necrosis, and reactive meningothelial hyperplasia

Morphologic and immunohistochemical features in this mass are consistent with a diagnosis of oligodendroglioma. While these tumors are relatively common in the cerebrum, spinal oligodendrogliomas are relatively rare. A specific cause for the massive hemorrhage and cavitation in this sections was not identified, but would presumably be attributable to vascular disruption (compression or infiltration) by the neoplasm. The neoplastic population was relatively well-differentiated, although there was evidence of significant invasive behavior.

Some conference participants suggested that disruption of the ventral median artery would be a likely cause for the distribution of hemorrhage. One conference participant suggested an embolic process, possibly distinct from the tumor (e.g. fibrocartilaginous embolism) as an etiology for the hemorrhagic focus. This was considered possible, although degenerative disc disease was not identified in this patient. We thank Dr. Linda Lowenstine and Dr. Kevin Woolard for their contributions to the review of this case.

Higgins, R. J., Bollen, A. W., Dickinson, P. J. and Sis-Llonch, S. (2016) Tumors of the Nervous System, in Tumors in Domestic Animals (ed D. J. Meuten), John Wiley & Sons, Inc., Hoboken, NJ, USA. doi: 10.1002/9781119181200.ch19.

Mamom T, Meyer-Lindenberg A, Hewicker-Trautwein M, Baumgartner W. 2004. Oligodendroglioma in the cervical spinal cord of a dog. Vet Pathol 41(5):524-526.

Pancotto TE, Rossmeisl JH, Zimmerman K, Robertson JL, Were SR. 2013. Intramedullary spinal cord neoplasia in 53 dogs (1990-2010): Distribution, clinicopathologic characteristics, and clinical behavior. J Vet Intern Med 27:1500-1508.