Successful surgical excision of periaortic hemangiosarcoma in a dog

Abstract

This report describes the management and outcome of periaortic hemangiosarcoma in a dog. An 8-year-old neutered male Siberian husky was referred for surgical intervention for an incidentally diagnosed caudal mediastinal mass. The dog was initially admitted for total ear-canal ablation due to a chronic unresolved left otitis externa/media. A head and chest CT scan obtained before surgery revealed an incidental, but large, caudal mediastinal mass. This scan also incidentally included most of the abdomen and showed no primary abdominal lesions. The dog underwent surgical excision of the caudal mediastinal mass 8 d after the CT scan. Surgery consisted of a lateral thoracotomy to excise the caudal mediastinal mass before considering surgical treatment of the ear. Complete surgical excision of the periaortic mass was completed. Histopathology revealed a diagnosis of hemangiosarcoma. The owners declined chemotherapy and the dog was euthanized 86 d later because of owner-perceived declining quality of life.

Key clinical message:

This case report describes, for the first time, successful surgical management and outcome for periaortic hemangiosarcoma. We propose that surgical excision of this type of mass is possible in a clinical setting, with prognosis similar to that for other visceral hemangiosarcoma.

CASE DESCRIPTION

An 8-year-old neutered male Siberian husky dog weighing 25.5 kg was brought to Veterinary Referral Associates (Gaithersburg, Maryland, USA) for evaluation of a chronic otitis externa of the left ear that persisted despite medical management for 9 mo before presentation. Otoscopic evaluation confirmed a mass in the left horizontal ear canal. On presentation to the surgery service, a CT scan of the dog’s skull and thorax was recommended to evaluate the extent of the mass and evaluate for metastatic lesions before a total ear-canal ablation.

At presentation, physical examination revealed erythema and discharge in the left ear, and otoscopic evaluation confirmed a raised, pink mass within the horizontal canal. Results of the remainder of the physical examination were within normal limits. Complete blood (cell) count was unremarkable. Serum chemistry abnormalities included increased concentrations of alkaline phosphatase (295 IU/L; reference range: 23 to 212 IU/L) and cholesterol (360 mg/dL; reference range: 110 to 320 mg/dL). The dog underwent skull and thoracic CT for presurgical planning and staging. The CT scan incidentally revealed a large (7.0 cm × 4.0 cm × 5.5 cm), lobular, hypoattenuating, peripherally contrast-enhancing mass ventral to the aorta and immediately ventromedial to right caudal lung lobe (Figure 1). The remainder of the thorax was unremarkable on CT scan. The head CT scan revealed a poorly defined, soft-tissue-attenuating, heterogeneously contrast-enhancing lesion within the left horizontal external ear canal, with the deep portion of the lesion penetrating medially into the left tympanic bullae. Primary differential diagnoses for the caudal mediastinal lesion, based on review of the CT scan by a Board-certified radiologist, included a probable paraesophageal empyema or abscess, with hematoma, granuloma, and neoplasia considered less likely. Primary differential diagnoses for the ear mass included aural polyp and neoplasia (ceruminous gland adenoma or carcinoma). Based on these CT results, the intrathoracic lesion became the primary clinical concern, with treatment directed at resolving the possible paraesophageal empyema or abscess.

FIGURE 1.

Sagittal plane CT (A) and transverse plane CT (B) images of the dog’s lobular, hypoattenuating, peripherally contrast-enhancing mass lesion (arrows) within the caudal dorsal mediastinum, immediately ventral-medial to the right caudal lung lobe and ventral to the aorta. Window width: 383 HU; window level: 24 HU; thickness: 2.0 mm; acquired with 100 kVp.

CD — Caudal; CR — Cranial; D — Dorsal; L — Left; R — Right; V — Ventral.

Surgery was a standard right lateral thoracotomy at the 9th intercostal space. Thoracic exploration revealed approximately 600 mL of hemorrhagic effusion that was evacuated from the thorax. A whole-blood transfusion was administered during surgery due to moderate hemorrhage and hypotension. No abscess was appreciated. A large, firm, dark-red mass was identified within the caudal mediastinum with a large associated hematoma; and mature, firm adhesions were noted along the length of the descending aorta. The mass was carefully dissected from the aorta with a combination of blunt dissection, bipolar electrocautery, and a vessel-sealing device (Precise Ligasure; Covidien, Mansfield, Massachusetts, USA). Based on the location of the mass, marginal resection was required and the mass was removed en bloc. No further hemorrhage was appreciated. The thoracic cavity was copiously lavaged with sterile saline, and oxidized cellulose (Surgicel Original; Ethicon, Neuchatel, Switzerland) was placed over the site of mass excision. A MILA chest tube (MILA International, Florence, Kentucky, USA) was placed within the 7th intercostal space using the modified Seldinger technique. The thorax was closed in routine fashion via circumcostal sutures followed by a standard 3-layer closure. The dog recovered uneventfully from the procedure and was discharged 36 h following surgery. Histopathological examination revealed the mass to be a periaortic hemangiosarcoma. The neoplastic cells abutted the surgical margin at many points, separated by variably thick, fibrous capsule. The dog was reexamined at 2 wk after surgery and was doing clinically well, with no overt complications. At that time, further follow-up with a medical oncologist for chemotherapy was recommended but was declined by the owners. Follow-up inquiry with the referring veterinarian revealed that the dog was euthanized 86 d later due to owner-reported concern for declining quality of life at home.

DISCUSSION

This report describes the first documented successful surgical treatment of a periaortic hemangiosarcoma in a dog. Periaortic hemangiosarcoma is extremely rare in dogs, with only 1 previous case documented, in a Norwich terrier (1). In that case, no treatment was undertaken because the dog died before any attempted intervention. Diagnosis in that case was based on postmortem evaluation. Hemangiosarcoma is an aggressive neoplasm of mesenchymal (endothelial) origin that is widely recognized to be more common in large-breed, older dogs. Labrador retrievers, golden retrievers, and German shepherds are considered breeds with a predisposition, but any breed or age of dog can be affected (2). Hemangiosarcoma is classically divided into 2 major subtypes according to location: visceral and non-visceral. Non-visceral hemangiosarcoma (cutaneous, subcutaneous, muscle) can have a better overall prognosis, with surgical excision being potentially curative in Stage 1 (dermal involvement only); whereas more advanced forms (Stages 2 and 3) of non-visceral and visceral hemangiosarcoma tend to behave more aggressively, with early metastasis and a poor long-term prognosis (2–6). The most common primary site of hemangiosarcoma is the spleen (2). However, visceral hemangiosarcoma can occur in the heart (most commonly in the right atrial appendage), pericardium, liver, kidneys, uterus, genitourinary tract, prostate, retroperitoneal space, bone, brain, lungs, and omentum (2,3,5). Reported median survival time (MST) for visceral hemangiosarcoma with surgery alone is ~19 to 86 d, with a 1-year survival rate of < 10% (2,3,5). Chemotherapy is recommended in all cases due to the aggressive nature of the tumor and high incidence of microscopic metastatic disease at the time of surgery. Doxorubicin is the most-clinically cited chemotherapeutic drug used in these cases in the absence of cardiac disease (2,3,5,6). Other chemotherapeutic drugs, including carboplatin, cyclophosphamide, vincristine, methotrexate, and epirubicin, have been investigated, and a definitive superiority has yet to be established for adjunctive management of hemangiosarcoma in dogs (2,5,6). With surgery and adjunctive chemotherapy, the MST increases to 141 to 179 d, though these times vary depending on the source (2,5). Regardless, even with adjunctive chemotherapy, the 1-year MST is still about ≤ 10% (2).

The periaortic location of the mass in the case reported here was a rare site for a presumed-primary hemangiosarcoma lesion, with only 1 previously documented case (1). The CT scan obtained before surgery did allow coverage of most of the abdomen and there was mild mottling of the spleen and a right-sided renal cortical cyst, but there was no overt primary neoplastic lesion in any of the other common sites for visceral hemangiosarcoma. However, as that presurgical CT scan was not set to image the abdomen in its entirety, full abdominal staging before surgery was not completed. This means we could not completely rule out a primary hemangiosarcoma lesion caudal to the level of the L4 vertebrae (where the CT scan stopped). Notwithstanding this, no clinical signs were noted before surgery that would indicate organ dysfunction elsewhere, aside from the left ear. The aural mass was never treated surgically following thoracotomy and, though aural hemangiosarcoma has not been previously reported, it cannot be ruled out as a primary hemangiosarcoma lesion at this time.

The hemothorax that was present at surgery occurred due to spontaneous hemorrhage. The CT scan was obtained ~8 d before surgery and did not detect any pleural effusion. There was no additional diagnostic testing before surgery that could be reasonably expected to cause the lesion to hemorrhage, and a recent study showed that hemangiosarcoma was associated with nontraumatic cavitary bleeding (7). Hemangiosarcoma was diagnosed in ~75% of dogs that were presented with nontraumatic hemoabdomen (7). In addition to the hemothorax noted in the other documented case of periaortic hemangiosarcoma, it may be reasonable to conclude that hemangiosarcoma should be a consideration in any case of nontraumatic hemothorax, particularly if a mass lesion is present (1,7).

Based on this report and the similar location and appearance of the mass noted in the only other reported case, hemangiosarcoma should be considered as a differential diagnosis in cases of caudodorsal mediastinal extrapleural mass lesions in the future. This case also demonstrated that periaortic hemangiosarcoma may be surgically resected for palliative purposes, with prognosis similar to that for visceral hemangiosarcoma elsewhere in the body.

A successful clinical outcome following surgical treatment of periaortic hemangiosarcoma has not been reported in small animals before this case report. However, this mass was identified incidentally and the dog was not initially presented with clinical hemothorax, making a planned surgical excision a viable option. As such, variation in outcome and anesthetic risks may be expected for animals presented with clinical bleeding. However, the risk of hemothorax is an important consideration in presurgical planning, as both this dog and the one in the previous case report had hemorrhage reported as a consequence of the periaortic hemangiosarcoma. In this case, the dog lived for 86 d without any further treatment. Additional studies would be necessary to determine if postoperative chemotherapy would extend the lifespans of dogs with periaortic hemangiosarcoma similar to those for other visceral hemangiosarcoma. CVJ