Angioleiomyosarcoma in the Nasal Vestibule of a Dog: Surgical Excision via a Modified Lateral Approach

Introduction

Nasal tumors account for approximately 1% of all reported neoplasia in the dog and are diagnosed primarily in older large-breed dolichocephalic dogs.¹ Epithelial tumors are common and include adenocarcinoma, squamous cell carcinoma, and undifferentiated carcinoma. Approximately one-third of nasal tumors are mesenchymal in origin and include chondrosarcoma, fibrosarcoma, osteosarcoma, hemangiosarcoma, and undifferentiated sarcomas. Nasal mesenchymal tumors are locally invasive, with low metastatic rates at the time of initial diagnosis.²

Angioleiomyosarcomas are rare perivascular wall tumors of nonendothelial origin derived from smooth muscle cells within the tunica media of the wall of blood vessels.³ Those tumors are well described in people. Descriptions of angioleiomyosarcomas in people and animals are rarely reported in locations other than the skin.^3,4 The benign form of this tumor, angioleiomyoma, has been reported occasionally in the nasal cavity of people.⁵

Most nasal tumors in dogs are malignant, locally invasive, and poorly responsive to surgical excision as a sole treatment. Curative surgical excision of canine nasal tumors, when attempted, is commonly approached either via dorsal or ventral rhinotomy. A lateral rhinotomy is a simple technique used to access lesions of the rostral nasal vestibule; however, description of this technique is limited in the veterinary literature.^6,7

This case report describes the clinical presentation, diagnostic evaluation, histological, and immunohistochemical diagnosis of an angioleiomyosarcoma in the rostral nasal cavity of a dog. It highlights the benefits of careful preoperative diagnostic evaluation and surgical planning, which led to successful treatment of the dog. Curative surgical excision using a modified lateral approach is described.

Case Report

An 11 yr old spayed female German shepherd dog weighing 42 kg presented to the university teaching hospital with a 6 mo history of intermittent epistaxis from the left nostril. Increased frequency of epistaxis had recently been observed, and the owners had noted progressive onset of stertorous breathing. On visual examination, a nonulcerated polypoid mass was evident within the left nares. Airflow was absent through this nostril. The remainder of the physical examination was normal. Three-view thoracic radiographs provided by the referring veterinary clinic revealed no abnormalities.

A complete blood cell count demonstrated a marginal leukocytosis (WBCs, 14.2 × 10⁹/L; reference range, 5.2–14 × 10⁹/L) characterized by a mild mature neutrophilia (11.3 × 10⁹/L; reference range, 3.9–8 × 10⁹/L). Leukocyte morphology was unremarkable. The dog had a mild thrombocytosis (410 × 10⁹/L; reference range, 143–300 × 10⁹/L) with normal platelet morphology. All red blood cell parameters were within normal limits. No significant abnormalities were detected on serum biochemical analysis, and coagulation parameters (prothrombin time and activated partial thromboplastin time) were within normal limits. Urinalysis was normal, and urine culture was negative for bacterial growth.

Computed tomography (CT)^a of the nasal cavity revealed a small contrast-enhancing, soft-tissue mass located at the rostral aspect of the left side of the nasal cavity (Figure 1). The mass appeared to have a 15 mm diameter base arising from the ventrolateral mucosal margin at the level of the root of the left maxillary canine tooth (204).¹⁷ The mass appeared to completely obstruct the left nasal cavity at the level of the rostral margin of the nasal bone. There was mild displacement of the septum at that level, but no evidence of either involvement or invasion of adjacent soft tissues or bony structures. There was mild turbinate atrophy immediately caudal to the mass. The remaining structures and turbinates of the nasal cavity were normal.

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On rhinoscopic examination, the right nasal cavity appeared normal. The left middle nasal meatus was obstructed by a pale, slightly irregular mass. Blood vessels were evident on the surface of the lesion. The mass originated approximately 30 mm from the external nares and extended caudally for 25 mm. Multiple biopsies were collected from the mass by traction pinch biopsy and were submitted for histopathological examination and aerobic bacterial and fungal culture.

Aerobic bacterial culture yielded a pure heavy growth of Pasteurella multocida with a wide spectrum of antibiotic sensitivity. Histopathological examination of the nasal biopsies revealed a densely cellular proliferation of neoplastic spindle cells that markedly expanded and effaced the lamina propria and submucosa. The neoplastic cells were arranged in whorls and bundles, which radiated from the tunica media of small blood vessels (Figure 2A) and were separated by a moderate amount of lightly eosinophilic fibrillar stroma. The mitotic index was 2.

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A diagnosis of a grade 1 soft tissue sarcoma was made and a perivascular wall tumor was suspected based on the morphologic features. Immunohistochemical staining was performed using antibodies for α-smooth muscle actin (1:75 dilution)^b, desmin (1:400 dilution)^c, myosin (1:2500 dilution)^d, and factor VIII-related antigen (1:200 dilution)^e. Over 90% of the neoplastic cells were immunoreactive for α-smooth muscle actin (Figure 2B) and positive immunolabeling of endothelial cells for FVIII-related antigen accentuated vascular lumina (Figure 2C). Further immunohistochemistry revealed strong, diffuse immunoreactivity for smooth muscle myosin (Figure 2D) and multifocal expression of desmin. That immunolabeling pattern was consistent with smooth muscle differentiation confirming the diagnosis of angioleiomyosarcoma.

Surgical exploration and/or referral to a radiation oncologist was recommended; however, the owner declined. Four months after initial diagnosis, the nasal mass remained present on rhinoscopic examination and intermittent epistaxis persisted. A marginal surgical excision using a modified lateral approach to obtain a small disease-free margin followed by fulguration of the wound bed was planned.

The dog was premedicated with methadone^f (0.3 mg/kg intramuscularly). Anesthesia was induced with diazepam^g (0.2 mg/kg IV) and propofol^h (1.7 mg/kg IV) and maintained with isofluraneⁱ in O₂ and nitrous oxide via a 10 mm cuffed endotracheal tube. A local infraorbital nerve block was performed using bupivacaine^j 0.3mg/kg. Crystalloid fluids^k were administered at 10 mL/kg/hr throughout surgery. The dog was placed in sternal recumbency with the head tilted to the right, and the nose was prepared for aseptic surgery.

The lateral approach to the nasal cavity was a modification of the approach described by Holt et al. (1990).⁷ The left rostral nasal vestibule was approached with a curved electrosurgical skin incision from the left lateral nasal fissure to past the level of left upper canine tooth (204) root^l (Figure 3A). The incision was continued through the subcutaneous and fascial layers into the ventral meatus with electrosurgery. Hemorrhage was controlled with electrocoagulation using a monopolar electrode. The incision was extended through the dorsolateral nasal cartilage and into the periosteum of the incisive bone and craniodorsal maxilla (Figure 3B). The soft tissues were elevated from the bone with a Freer elevator. Double action rongeurs were used to remove dorsolateral incisive and maxillary bone to the level of the root of the left maxillary canine tooth (204). The canine tooth root was not exposed. That approach achieved a wide exposure to the rostral nasal vestibule (Figure 3C). A 25 mm pedunculated mass was identified arising from the ventrolateral wall of the ventral meatus. The mass was excised at its base using electrosurgery. The excision included the mucosa, the underlying ventral lateral cartilage, and adjacent turbinates to a level approximately 10 mm deep to the ventral margin of mass, which resulted in a 30 mm circular defect in the nasal mucosa. The excision site was lavaged with ice-chilled saline and fulgurated using the monopolar electrode to achieve hemostasis. Minimal hemorrhage was experienced. Primary closure of the mucosa over the ablated tissue bed was not possible. The rostral nasal mucosa was apposed with 3-0 polydiaxonone^m simple continuous sutures. The subcutaneous tissues were closed similarly. The skin was apposed with 4-0 poliglecaproneⁿ intradermal sutures.

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The dog recovered uneventfully from surgery. IV crystalloid fluids^o were continued until the dog was fully recovered and was eating and drinking. Methadone (0.3 mg/kg IV q 6 hr) was administered for analgesia for the first 18 hr postsurgically. Tramadol^p (2 mg/kg intramuscular q 12 hr) was commenced immediately after surgery. The dog was discharged from hospital the day after surgery with oral tramadol^q (2 mg/kg per os q 8–12 hr) and meloxicam^r (0.1 mg/kg per os q 24 hr). At the recheck examination 10 days after surgery, the skin incision was healed. The owner reported the dog had not had any sneezing or epistaxis since discharge.

Histopathological examination of the excised tumor revealed similar morphologic features noted in the previous biopsy, although a mild increase in cellular atypia and disorganization within the tumor was noted. Neoplastic cellular infiltrates were present within the mucosal tissue at the base of the mass; however, there was no evidence of neoplastic penetration into the excised turbinates and neoplastic cells did not extend within at least 2 mm of the surgical margin.

The dog re-presented 12 mo postsurgically. The owner reported the dog to be behaving normally with no episodes of sneezing or epistaxis. The cosmetic appearance was excellent. Airflow was apparent through both nostrils. A CT of the nasal cavity showed no evidence of tumor regrowth (Figure 4). The dog remains free of clinical signs of recurrence at 28 months after surgery.

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Discussion

This case report describes the electrosurgical excision of an angioleiomyosarcoma from the rostral left nasal cavity of a dog. The lateral surgical approach to the left ventral meatus provided adequate exposure for complete mass excision (based on histological margin examination). Twelve months postsurgically, there was no evidence of tumor regrowth on nasal CT and the dog was free of clinical signs of nasal disease 28 mo postsurgically.

Angioleiomyosarcomas are categorized as a subgroup of soft tissue sarcomas known as perivascular wall tumors.⁸ Perivascular wall tumors are a distinct group of nonendothelial vascular wall neoplasms that may arise either from pericytes lining the endothelial cells of capillary walls or perimyocytes/myocytes of the smooth muscle within the walls of larger blood vessels.^3,9 The scarcity of smooth muscle within the nasal cavity makes it an unlikely location for that type of neoplasm.⁵ Descriptions of angioleiomyosarcomas in people and animals predominately report cutaneous neoplasia.^3,4 In people, case reports involving angioleiomyosarcomas associated with the pulmonary artery, femoral artery, omentum, ureter and kidney, and nasal cavity have been published. Carpenter and Hamilton (1995) reported a case of an angioleiomyoma in the nasopharynx of a dog and Kheirandish et al. (2010) published a case of periorbital angioleiomyosarcoma in a dog.^10,11

Perivascular wall tumors have only recently been characterized in the dog following reclassification of hemangiopericytomas according to histological and immunohistochemical characteristics.^3,8 Differentiation of angioleiomyosarcoma from its benign form is based on the presence of cytological atypia, increased mitotic rate, and invasive or expansile growth patterns.^3,4 Immunostaining with Factor VIII and smooth muscle actin allowed further characterization of the low-grade soft tissue sarcoma to make a definitive identification of an angioleiomyosarcoma.

CT was important for planning the surgical approach to the tumor in this dog. The accurate localization of the origin of the mass from the ventrolateral mucosal margin within the rostral aspect of the left nasal cavity and characterization of its appearance as pedunculated without evidence of invasion into the surrounding soft tissue or bony structures was pivotal in the decision to proceed via a lateral rhinotomy.

The lateral rhinotomy described herein was simple to perform. It provided good visibility and access to the nasal meatus, which was not accessible by standard dorsal or ventral rhinotomy approaches. The lateral approach was considered to be less invasive and carry less potential postoperative morbidity than either removal of the palatine bone via a ventral approach or the creation of a nasal bone flap in a dorsal rhinotomy. The described approach was modified from the procedure as previously described, with extension of the lateral exposure by removal of the dorsolateral incisive and maxillary bones to the level of the rostral border of the left maxillary canine tooth (204).^7,12 The selected approach improved exposure of the base of the tumor, did not cause overt postoperative morbidity, and still allowed a cosmetic wound closure.

The surgical approach was made using electrosurgery to minimize hemorrhage in the surgical field and maximize visualization. Electrofulguration of the wound bed was performed in this case. Fulguration resulted in superficial desiccation and charring to the wound bed (<2 mm), extending the deep margin of excision beyond the incised margin, and allowing control of hemorrhage from the wound bed because primary tissue apposition was impossible.¹³

There are no guidelines published on the required margin of surgical excision needed for nasal tumors of this type, and an assumption is made that they behave similarly to other mesenchymal tumors (e.g., leiomyosarcomas and soft tissue sarcomas).¹⁴ Perivascular wall tumors are considered locally aggressive, slow growing, and slow to metastasize. As for other soft tissue sarcomas, complete surgical excision is considered the treatment of choice, with adjunct radiation therapy in cases of either planned marginal excision or incomplete excision.^1,15,16 A recent study of cutaneous perivascular wall tumors in 55 dogs, however, concluded that those tumors represent a unique subgroup of soft tissue sarcoma that have a low to nonaggressive behavior and a low tendency to metastasize (<4% in that study).⁸ Local recurrence occurred only after a prolonged latency period, with an increased risk of recurrence with each 1 cm increase in tumor size.⁸ There was no evidence of an association between histological grade and surgical margin with tumor recurrence. No perivascular wall tumor with clean surgical margins (>3 mm) recurred within the study period (median follow-up time, 665 days).

Postcontrast CT performed 12 mo postsurgically on the dog in this case report confirmed the absence of tumor regrowth, indicating local excision alone had been effective for that time period. The dog remains free of clinical signs of nasal disease 28 mo after surgery. Based on those features, evidence of clean surgical margins, and assuming nasal angioleiomyosarcomas behave similar to other perivascular wall tumors, the study authors consider the dog cured of the disease.

Conclusion

The diagnostic approach used in this case provided definitive identification of tumor type and location, allowing specific preoperative planning of a surgical approach to achieve curative excision of the nasal mass. The lateral approach to the rostral nasal vestibule used in this dog was simple to perform, provided good exposure of the nasal mass, and resulted in an excellent cosmetic outcome. The described approach should be considered for either biopsy or excision of any well-defined lesions in the rostral nasal cavity of the dog.