A Review of Proliferative Vascular Disorders of the Central Nervous System of Animals

Abstract

In disease, blood vessel proliferation has many salient roles including in inflammation, when granulation tissue fills superficial defects, or in the recanalization of an occluded blood vessel. Sometimes angiogenesis goes awry—granulation can be exuberant, and plexiform proliferation of vascular components can contribute to pulmonary hypertension. This review focuses on the diverse manifestations of pathologic vascular overgrowth that occur in the brain, spinal cord, and meninges of animals from birth until old age. Entities discussed include systemic reactive angioendotheliomatosis in which glomeruloid vascular proliferations are encountered in various organs including the central nervous system (CNS). The triad of CNS vascular malformations, hamartomas, and benign vascular proliferations are an especially fraught category in which terminology overlap and the microscopic similarity of various disorders makes diagnostic classification incredibly challenging. Pathologists commonly take refuge in “CNS vascular hamartoma” despite the lack of any unique histopathologic features and we recommend that this diagnostic category be abandoned. Malformative lesions that are often confusing and have similar features; the conditions include arteriovenous malformation, cavernous angioma, venous angioma, and capillary telangiectases. Meningioangiomatosis, a benign meningovascular proliferation with dual components, is a unique entity seen most commonly in young dogs. Last, accepted neoplastic conditions range from lower-grade locally acquired growths like hemangioblastoma (a tumor of mysterious interstitial stromal cells encountered in the setting of abundant capillary vasculature proliferation), the rare hemangioendothelioma, and the highly malignant and invariably multifocal metastatic hemangiosarcoma. Additionally, this review draws on the comparative medical literature for further insights into this problematic topic in pathology.

Encephalic meningioangiomatosis in a cat

“…2,9 However, the meningovascular nature of the lesion with characteristic subarachnoid and neuroparenchymal arrangement of spindle cells around blood vessels is not typical of meningioma, and should suffice for a histologic diagnosis of MA. 16 Although IHC has limited diagnostic value in human and veterinary cases, 10,15 the immunolabeling profile in our case was also consistent with cases of MA described previously in humans and dogs. 5 The robust immunolabeling for vimentin has been reported consistently in MA, supporting a mesenchymal origin for the proliferated spindle cells.…”

“…2 The local invasion into the neuroparenchyma can be destructive and induce gliosis, neuroaxonal degeneration and necrosis, and gray or white matter necrosis. 10 In our case, extensive astrogliosis and microgliosis was present within the surrounding neuroparenchyma.…”

“…2,19 Although developmental and dysplastic mechanisms have been proposed, the pathophysiology and histogenesis of MA remain widely elusive in human and veterinary medicine. 10,19 The characteristic lesion of MA consists of a proliferation of meningothelial and spindle cells (presumably meningeal fibroblasts) that efface the subarachnoid spaces and typically extend along the perivascular spaces into the outer encephalic or spinal cord neuroparenchyma. 2,6,15 MA was first described in humans in 1915 and has been reported in nearly 200 patients.…”

Epidural myelolipoma in a Silken Windhound

“…On the T1‐weighted sequence, the mass displayed a medium signal intensity (hyperintense to the spinal nerves and hypointense to the surrounding fat) and no contrast enhancement after intravenous gadolinium administration. Differentials included hemorrhage, extramedullary hematopoiesis, vascular malformation, 2 lipoma or angiolipoma, 3 and malignant neoplasia such as hemangiosarcoma 4…”

Special focus on diagnostic veterinary oncologic pathology

“…This review codifies our knowledge on this challenging group of lesions and offers simplistic ways to separate the entities utilizing histochemical and immunohistochemical stains. 15 Publication of the works herein would not have been possible without the dedicated editorial and administrative staff at Veterinary Pathology. We hope that the reader enjoys this collection of articles and is able to use them in their diagnostic practice.…”