Piecemeal endoscopic polypoidectomy for the management of a canine pharyngeal hemangiosarcoma

Abstract

A 7-year-old castrated male Maltese dog was presented for increased respiratory sounds, inability to bark, dysphagia, and hyporexia. Radiographs revealed an ovoid, opaque mass in the caudal nasopharynx. An airway examination and computed tomography scan were followed by endoscopic polypoidectomy. The mass was a hemangiosarcoma, and the patient survived > 13 months.

Case description

A 7-year-old castrated male, 3.8-kg Maltese dog was presented to the Texas A&M Veterinary Medical Teaching Hospital (VMTH) with a 2-week history of mildly increased respiratory sounds, inability to bark, mild dysphagia, and hyporexia. Empirical therapy with diphenhydramine (unknown dose) and amoxicillin, 15 mg/kg body weight (BW), PO, q12h, for 10 d had not mitigated the clinical signs.

Physical examination did not detect any abnormalities, and results of routine hematologic and biochemical analyses were within reference ranges. Thoracic radiographs taken 3 d previously by the referring veterinarian were available for review (Figure 1), and indicated an approximately 1.1 × 3.7 cm ovoid soft tissue opaque mass in the caudal nasopharynx. The cranial margin of the mass had a curved soft tissue/gas interface indicating an intraluminal location. Differential diagnoses for the mass included a polyp, abscess, foreign body with associated cellulitis, neoplasm, and cyst.

Figure 1.

Ventrodorsal and right lateral radiographic views of the nasopharynx of a 7-year-old castrated male Maltese dog with a 2-week history of mild dysphagia, inability to bark, and hyporexia. There is an ovoid, soft tissue opaque mass within the caudal nasopharynx (arrow).

The dog was sedated with butorphanol (Vetorphic; MWI Animal Health, Boise, Idaho, USA), 0.2 mg/kg BW, IV, and anesthesia was induced using propofol (PropoFlo; Abbott Animal Health, Abbott Park, Illinois, USA), 5 mg/kg BW, IV. Upper airway examination with a rigid laryngoscope revealed a multi-lobulated mass at the level of the right tonsillar arch. The patient was intubated using a 4.5-mm ID 19-cm cuffed endotracheal tube. Dexamethasone (Azium; Schering-Plough Animal Health, Union, New Jersey, USA), 0.1 mg/kg BW, IV, was administered to reduce airway inflammation. A computed tomography (CT) scan of the cervical region was performed with the patient positioned in dorsal recumbency. This revealed an ovoid, soft tissue attenuating, heterogeneously contrast-enhancing, broad-based mass (2.5 × 1.3 × 1.1 cm) within the caudal nasopharyngeal region (Figure 2). This mass was causing almost complete occlusion of the caudoventral aspect of the nasopharynx, with extension into the laryngopharynx. A 4.9-mm flexible endoscope (Olympus BF-P180 bronchovideoscope; Olympus, Center Valley, Pennsylvania, USA) was directed into the pharynx, revealing a disorganized and somewhat pedunculated mass (Figure 3A). Adequate inflation of the endotracheal tube cuff was verified at this time. A 2-cm polypectomy snare (Olympus Gastroscope & Colonoscope Snare SD-24OU-15; Olympus) was placed around the base of the mass under direct observation and attached to an electrosurgical generator (Mega Power Generator; Megadyne Medical Product, Draper, Utah, USA) for simultaneous cutting and cautery. The settings on the electrosurgical generator were 15W and 20W for the cut and coagulation, respectively. Inhalant sevoflurane anesthesia and oxygen were discontinued briefly and the patient was allowed to breathe room air to reduce the risk of airway fire. A fentanyl bolus (Fentanyl; West Ward Pharmaceutical, Eatontown, New Jersey, USA), 3 μg/kg BW was used to maintain an adequate plane of anesthesia. A long curved hemostat was used to hold the free edge of the mass as the cutting and cautery progressed, to reduce the risk of damage to adjacent tissues and to facilitate tissue retrieval after resection. This procedure was repeated a total of 3 times (i.e., piecemeal resection), and approximately 80% of the mass was removed (Figure 3B). All 4 fragments were placed in formalin for histopathologic examination. The total procedural time was less than 45 min, and minimal bleeding was observed. The endotracheal tube was partially inflated during removal. Maropitant (Cerenia; Zoetis, Kalamazoo, Michigan, USA), 1 mg/kg BW, IV, and buprenorphine (Burprenex; Reckitt Benckiser Pharmaceuticals, North Chesterfield, Virginia, USA), 0.01 mg/kg BW, IV, were administered following extubation. Supplemental oxygen was not necessary during recovery. The dog was observed for 4 h after completion of the procedure and was discharged with liquid tramadol (Ultram; Janssen Pharmaceuticals, Titusville, New Jersey, USA), 4 mg/kg BW, PO, q8h, for the next 3 d.

Figure 2.

Transverse and sagittal computed tomography (CT) images. Of the nasopharynx of a Maltese dog with a 2-week history of mild dysphagia, inability to bark, and hyporexia. Note the heterogeneous, mildly contrast-enhancing, ovoid mass (arrows) present within the caudal nasopharynx, causing near complete occlusion of the nasopharyngeal lumen at this level.

Figure 3.

A — Endoscopic image of the disorganized pedunculated mass in the caudal nasopharynx at the level of the right tonsillar arch (top of the image is dorsal and the bottom of the image is ventral). B — Endoscopic image after 80% of the mass in the caudal nasopharynx had been removed with the polypectomy snare.

Histopathologic examination revealed an infiltrative, unencapsulated, poorly demarcated submucosal neoplasm, composed of spindle cells arranged in tight bundles and forming irregular, variably sized blood-filled vascular channels (Figure 4A). These findings were consistent with a histopathological diagnosis of a hemangiosarcoma, with extensive ulceration and incomplete excision. This diagnosis was confirmed with immunohisto-chemistry, as staining with Factor VIII Related Antigen showed moderate cytoplasmic immunolabeling of approximately 30% of the neoplastic cells (Figure 4B).

Figure 4.

A — The submucosa is markedly expanded by an unencapsulated, poorly demarcated, densely cellular, infiltrative neoplasm composed of spindle cells arranged in tight bundles and forming irregular, variably sized blood-filled vascular channels. [Hematoxylin & eosin (H&E) staining 20×]. B — Moderate cytoplasmic immunolabeling of approximately 30% of the neoplastic cells for von Willebrand factor (40×). Photographs courtesy Dr. Carolina P. Azevedo.

During a follow-up appointment with the oncology service, the owners declined chemotherapy or radiation therapy. No staging was done. On a 13-month post discharge follow-up phone call, the dog was reported to be doing well at home, without any clinical signs.

Discussion

Hemangiosarcoma (HSA) is a malignant tumor arising from the vascular endothelium and comprises approximately 5% to 7% of noncutaneous primary malignant neoplasms in dogs. The most common sites for HSA in this species are the spleen, right atrium, subcutaneous tissues, and liver (1). Median survival times (MSTs) for dogs with visceral and subcutaneous HSA are short, with less than 10% of dogs alive 1 y after diagnosis. Using a combination of surgery and chemotherapy for stage 1 disease (i.e., no evidence of tumor or the tumor is < 5 cm diameter and confined to primary site), MST is about 250 d. For stage II (i.e., the tumor can be < 5 cm, or greater or ruptured, or invading subcutaneous tissues with regional lymph node involvement), MST is about 186 d, and in stage III disease (i.e., the tumor may invade adjacent structures, including muscle, may or may not have lymph node involvement, but distant metastasis is present), MST is only 87 d (2,3).

Survival times for dogs with superficial dermal hemangiosarcomas treated surgically (1) are substantially better, with reported MSTs > 2 y, and 987 d (4). Oral cancer accounts for 6% to 7% of malignancies in dogs, and males have a 2.4 times greater risk of developing oropharyngeal malignancy than females (5). There is limited information regarding outcome for dogs with oral and pharyngeal HSA, but these may carry a better prognosis than the visceral or subcutaneous forms of this disease (6,7). One dog lived 220 d following incomplete excision and chemotherapy (7) for a pharyngeal HSA. The cause of death in this case was related to an inadvertent overdose of chemotherapy rather than the disease itself. It remains unknown if oral and pharyngeal HSA behave similar to superficial dermal HSA.

This report describes successful, palliative, per-oral debulking of a pharyngeal obstructive hemangiosarcoma using a polypectomy snare. Hemorrhage was minimal and the dog recovered quickly from the procedure. Disease-free margins are not expected in this location and the primary goal of the procedure was to improve patient comfort, collect tissue for histopathology, and facilitate a smooth recovery from anesthesia. A bipolar snare device was used in this case, as this was thought to reduce the risk of bleeding and perforation compared with a monopolar snare (8).

Endoscopic polypectomy of gastrointestinal tract masses has been described in veterinary medicine for inflammatory colonic polyps (9), benign colorectal polypoid adenomas (10), and gastric polyps (11). Endoscopic polypectomy using a bipolar snare has been described as an efficient and safe complementary method for the treatment of vocal cord polyps in humans (12). Endoscopic polyploidectomy and debulking did provide effective palliation (13 mo) in this dog with pharyngeal HSA.

To the best of our knowledge, this is the first report of endoscopic polyploidectomy for the management of pharyngeal hemangiosarcoma in a dog. These are uncommon tumors and carry a different long-term prognosis than visceral hemangiosarcoma, but debulking using endoscopic piecemeal polyploidectomy appears to be a useful palliative option. CVJ