Introduction

Angiomatosis is a rare vasoproliferative disorder, characterized by a mixture of blood vessels forming multiple angiomas mixed with adipose tissue lobules.¹ Angiomatosis is considered an infiltrative but nonneoplastic condition.²

Several forms of angiomatosis have been described in dogs, including cutaneous,^3–6 meningeal,^7–10 skeletal,¹¹ and multifocal forms.¹² However, canine vertebral angiomatosis has never been reported. This case report describes the clinical features, the diagnostic appearance, and the follow-up of a young dog with angiomatosis affecting a thoracic vertebra.

Case Presentation

A 3 yr old spayed female Cavalier King Charles spaniel was referred for 8 mo history of pain and reluctance to jump. The dog had received steroidal and nonsteroidal anti-inflammatory drugs, with mild improvement of the neurological signs. Three months before the presentation, the clinical signs progressed with hind limb gait abnormalities. The general physical examination was normal. Neurological examination showed marked pelvic limbs proprioceptive ataxia and paraparesis. Postural reactions were reduced in the left pelvic limb and absent in the right. Segmental spinal reflexes were normal. Marked pain was elicited on palpation of the thoracic vertebra. The clinical findings were consistent with a thoracolumbar (T3–L3) neuroanatomical localization of the lesion. The main differential diagnoses included degenerative, congenital, inflammatory/infectious, and neoplastic etiologies. The complete blood cell count and serum biochemical analyses were within normal limits. Thoracic radiographs revealed a radiolucent lesion affecting the vertebral body and the pedicle of the fifth thoracic vertebra. The dog underwent computed tomography (CT) and magnetic resonance imaging (MRI). General anesthesia was induced with a combination of methadone (0.2 mg/kg IV)^a and dexmedetomidine (1.5 mg/kg IV)^b and maintained with isoflurane. The CT^c was performed with a 16-slice CT, whereas MRI^d of the thoracolumbar vertebral column and spinal cord was performed using a 0.17 T magnet. Sequences included T1-weighted (T1W), T2-weighted (T2W), and short tau inversion recovery (STIR) images in transverse and sagittal planes. In addition, T1W images in sagittal and transverse were obtained after IV administration of paramagnetic contrast media gadoversetamide^e at 0.1 mmol/kg.

The CT showed focal osteolysis of the vertebral body and the pedicles of the fifth thoracic vertebra (T5) (Figure 1). Furthermore, hyperdense, extradural material was seen within the vertebral canal, causing moderate spinal cord compression on the right side. The material showed moderate heterogeneous contrast enhancement. The MRI confirmed, at the level of T5, an extradural lesion, hyperintense on T1W, T2W, and STIR images, with mild and irregular enhancement after contrast administration. The lesion compressed the spinal cord on the right side. The MRI also showed an abnormal morphology of the T5 vertebra and a mild hyperintense signal on T2W images within the spinal cord cranial to the mass consistent with spinal cord edema. Surgery was recommended to decompress the spinal cord and obtain biopsy samples for histological examination. However, the owners initially declined this option. At the time of re-evaluation, 6 mo after, the clinical condition had worsened, and the dog was paraplegic. Therefore, the owners elected to proceed with surgical decompression. A T4–T5 hemi-dorsal laminectomy was performed on the right side. A proliferative tissue was visible, with evidence of ventrolateral displacement of the spinal cord. The abnormal tissue was removed and submitted for histopathological examination. In addition, some bone fragments from the body of the T5 were collected and examined. Macroscopically, the biopsied tissue was 0.2 cm in diameter, yellowish, and with a firm consistency. The histopathological analysis showed an encapsulated, moderately cellular vascular proliferation, infiltrating the bone trabeculae and soft tissue. The proliferation consisted of a mixture of arterial and venous blood vessels admixed with small capillaries and collagenous stroma. Endothelial cells were disposed in a single layer and were characterized by indistinct margins, central oval nuclei, or paracentral with compact chromatin and inconspicuous nucleoli. Anisocytosis and anisocariosis were mild, and mitoses were rare (1 in 10 high power fields 2.73 mm²). The bone tissue appeared widely fragmented/necrotic and multifocally remodeled (Figure 2A,B). At the immunohistochemistry, the capillaries were diffusely and strongly positive for cluster of differentiation 31 antibody and factor VIII. The cells surrounding the capillaries were negative for neuron-specific enolase. These findings were consistent with a diagnosis of vertebral angiomatosis. Postoperative analgesia consisted of methadone (0.2 mg/kg q 4 hr IV) for the first 3 days. In addition, antibiotic medication (cephalexin 30 mg/kg q 12 hr per os [PO])^f was administered for 5 days. The dog was discharged 4 days after surgery with the following medications: tramadol (2 mg/kg q 8 hr PO)^g, omeprazole (0.75 mg/kg q 24 hr PO)^h, and firocoxib (5 mg/kg q 24 hr PO)ⁱ for 5 days. Postoperatively, the dog was paraplegic but improved over the following 2 wk becoming only mildly ataxic. The dog was re-evaluated 5 mo after surgery because her neurological status deteriorated. The neurological examination revealed nonambulatory paraparesis. A follow-up CT was performed showing a recurrence of the intracanal lesion. The owner refused a second surgery and elected euthanasia.

View Figure

• Download as Powerpoint
• Download Figure

View Figure

• Download as Powerpoint
• Download Figure

Discussion

Vertebral angiomatosis is considered a rare vascular malformation characterized by a proliferation of blood vessels with well-differentiated walls.¹

Other than vascular malformation, proliferative vascular disorders include reactive vascular proliferations and neoplastic lesions. Because they share several morphological features, the distinction between these categories is extremely challenging.¹ The pathogenesis of vertebral angiomatosis is not completely understood. It is nevertheless considered a nonneoplastic disorder.²

In human medicine, this disorder is also named hemangioma. The general population has an estimated incidence of 10–12%. Vertebral hemangioma is more often an incidental finding because only 1% of all cases have aggressive behavior and are symptomatic. The first symptom is often back pain, followed by chronic and progressive thoracic signs of myelopathy.¹³

In veterinary medicine, vertebral angiomatosis has been reported only in nine cats.^2,14–18 To the author’s knowledge, no previous cases were described in dogs. The lesion affected the thoracic vertebra in eight cats and the lumbar vertebra in one case. Similarly, the dog of the present description showed clinical signs before the age of 3 yr, and, as in feline angiomatosis, the signs were insidious and progressive, characterized by pain and difficulty walking, due to a thoracic lesion.^2,14–18

In human patients, neurologic signs may be caused by bony compression resulting from hypertrophy of the cortex, the vertebral body, the laminae, or the articular facet joints, but also results from soft-tissue extension of vertebral hemangioma into the epidural space.¹³ The latter feature reflects an aggressive behavior similar to the case here described.

The diagnosis of vertebral angiomatosis could be challenging. The radiographic features may resemble neoplastic diseases, like plasmacytoma, osteosarcoma, or metastatic disease.¹³ Radiographic studies do not distinguish between these diseases and only provide help in localizing the pathological site.¹³ In human medicine, vertebral hemangioma can be radiographically classified as typical, atypical, and aggressive.¹⁹ The “typical” and “atypical” forms refer to the MRI features and are influenced by the amount of adipose and vascular components and interstitial edema of the hemangioma. The aggressive form refers to vertebral hemangioma that are invading the epidural and paravertebral spaces.¹⁹ On CT, the aggressive form of vertebral hemangioma involves the vertebral body and arch. It is characterized by small, highly attenuated areas, representing thickened hyperdense trabeculae and surrounded by hypodense stroma, producing a polka-dot or honeycomb appearance.¹⁹

On MRI, vertebral hemangioma shows increased signal intensity on both T1W and T2W images with a hypointense area.²⁰ Usually, it is also slightly hyperintense on STIR and shows variable postcontrast enhancement.¹⁹ The imaging features in of our case are similar to the findings reported in humans. The diagnosis of vertebral angiomatosis was obtained by histological examination. Immunohistochemistry was performed to confirm the vascular origin of the lesion (cluster of differentiation 31 and factor VIII) and to rule out other rare vertebral neoplasms with vascular components, such as hemangioblastoma which is typically positive to NSE. Hemangiosarcoma was excluded because of the lack of significant atypia of endothelial cells, low mitotic count, and the overall microscopic architecture of the lesion.

In humans, several treatments have been reported including surgery, vertebroplasty, direct ethanol injection, radiotherapy, embolization of the feeding arteries, and a combination of these modalities.²⁰ There is, however, no consensus on the best treatment strategy for symptomatic cases. Surgery is indicated in cases of rapid clinical deterioration or progressive neurological symptoms.²⁰ Radiotherapy is used for patients with mild and slow progressive neurological deficits and reduces recurrence after subtotal tumor resection.¹⁹ In the veterinary literature, six cats were surgically treated.^2,16–18 Except for one cat who died shortly after surgery, all of them had an excellent outcome. In particular, a cat undergoing surgery and adjuvant radiation therapy showed no evidence of recurrence 26 mo after the initial diagnosis.¹⁸

The dog of this report rapidly recovered after the surgery but relapsed a few months later. In humans, clinical signs may recur when the tumor is only surgically treated. Therefore, in order to reduce the risk of relapse, postoperative irradiation is often used after incomplete or subtotal surgical decompression.^13,20 In veterinary medicine, the cat who underwent surgical decompression and radiation therapy had the longest follow-up without recurrence.²⁰ However, to date, there is insufficient data to recommend radiotherapy as an additional treatment in dogs and cats.

Conclusion

Vertebral angiomatosis is a rare condition in dogs and cats. However, the clinical and histopathologic features are similar in these two species. This condition should be considered a possible cause of insidious thoracolumbar myelopathy and/or back pain in young dogs. The MRI findings cannot distinguish vertebral angiomatosis from other neoplasms. Surgical treatment may lead to fast improvement. However, incomplete resection may lead to a recurrence of clinical signs.

The authors declare that informed consent was obtained from the pet owners. The patient was managed according to the standard of care described in the JAAHA policy statement.