Vascular Hamartoma as the Cause of Hind Limb Lameness in a Horse

Vascular hamartoma in horse limbs: presentation, diagnosis, and treatment of two case studies

Vascular hamartoma is an abnormal development of endothelial tissue that rarely affects horses. Histopathological examination remains the gold standard for definitive diagnosis, yet the presence of abnormal vascular structures must be carefully differentiated from other vascular anomalies and neoplasms. This report describes two cases of vascular proliferation affecting the skin on the lateral side over the left tarsus and the dorsolateral region over the fetlock joint of two fillies. The clinical history, presentation, and radiographic and sonographic findings in both patients suggested a neoplasm of unknown origin. Surgical excision of the mass was successfully performed in both patients. In one patient, a second surgery was performed six months after the first surgery because of the recurrence of the mass. Histopathological examination revealed a disorganized proliferation of well-differentiated, tortuous, and varied-sized blood vessels hemmed in myxoid tissue with abundant fibrocollagenous bands. Immunohistochemical examination of the endothelium markers factor VIII and ERG revealed positive staining of the mass samples in both cases, confirming their vascular origin. The combination of these markers was effective, providing a reliable option for differentiating vascular proliferation in horses. To the best of the author's knowledge, this is the first report applying the ERG endothelial marker to horse vascular malformations.

Perivascular wall tumour presenting as pastern mass in a Standardbred gelding

A 2-year-old Standardbred gelding was referred for a mass on the palmaromedial right front pastern which was accompanied by progressively worsening lameness. The mass was firm to palpation and covered by normal skin. Ultrasonographically, a smooth encapsulated mass was present, medial to the flexor tendons and palmar to the neurovascular bundle. Because of a poor prognosis for future athletic performance without surgical or chemotherapeutic intervention and economic constraints preventing further diagnostics and treatment, the horse was euthanised. Post-mortem magnetic resonance imaging, histopathology and immunohistochemistry revealed the mass to be a perivascular wall tumour, the first record of such a neoplasia in the horse.

Case report: Surgical treatment and long-term successful outcome of a spinal intramedullary vascular malformation in a dog

A 3.5-year-old male intact Staffordshire terrier crossbreed dog was presented with a one-week history of progressive paraparesis with fecal and urinary incontinence. Neurological examination was consistent with a T3-L3 myelopathy. A magnetic resonance imaging study revealed the presence of a well-circumscribed hemorrhagic space-occupying lesion at the level of T12, suspected to be a vascular malformation, such as cavernoma or arteriovenous fistula, primary hematoma or hamartoma; less likely considerations included hemorrhagic inflammation or hemorrhagic primary or secondary neoplasia. A dorsal laminectomy, durotomy, and midline dorsal myelotomy were performed with a surgical microscope, and the vascular lesion was identified and removed. Histological examination of surgical samples yielded fibrin, hemorrhage, hematoidin pigment, and some neural tissue. Although a lining wall was visualized during surgery consistent with a vascular malformation, there was no histological confirmation of such a structure, hampering definitive classification of the lesion. There was no gross or histopathological evidence that would support a diagnosis of a hamartoma or benign neoplasia. The dog was paraplegic with intact nociception the day following surgery. Ambulation was recovered within 2 weeks. Progressive and complete recovery of neurological function was seen over the next 12 weeks. No recurrence of neurological dysfunction was seen over a 12-month follow-up period. Surgical treatment should be considered in dogs with spinal intramedullary vascular lesions which can have a successful long-term outcome.

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

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.

Surgical removal of a localised vascular hepatic hamartoma in a dog

A 2-year-old male Labrador Retriever was presented for sudden abdominal distension. Abdominal ultrasonography revealed abundant abdominal fluid and a hepatic mass, which was removed by total lobectomy. Histologic evaluation of the mass supported a vascular hepatic hamartoma. Vascular hamartomas are rare malformations in animals and only two cases have been reported in the dog. This is the first recorded case of a canine vascular hepatic hamartoma treated surgically and having a successful long-term outcome.

A vascular hamartoma arising from the cervical spine of a cat

A 15-month-old cat presented for evaluation of worsening generalized proprioceptive ataxia. Computed tomography of the cervical spine revealed the presence of a compressive extradural bony mass involving the dorsal aspect of C1. Surgical exploration and debulking of the mass was performed. Histological evaluation of the mass revealed fibrovascular tissue consistent with a vascular hamartoma. This mass was deemed to be originating from the soft tissue associated with the C1 vertebra with subsequent bony proliferation. Surgical debulking of the mass resulted in complete resolution of clinical signs with no evidence of recurrence 2 years after surgery.