Veterinary Medicine - November 2008 - (Page 608)

A challenging case PEER-REVIEWED 4. An intraoperative view of blunt dissection of the mass from the muscular layer with Metzenbaum scissors. Stay sutures are present in the adventitial and muscularis layer. 5. An intraoperative view after enucleation of the mass and closure of the esophagus. or were greatly improved. Additional follow-up was recommended if any further clinical signs were noted. DISCUSSION Esophageal tumors account for less than 0.5% of all canine neoplasms.1 Most esophageal tumors occur in older animals, and they are often malignant. The most commonly reported primary esophageal tumors are sarcomas (osteosarcoma and brosarcoma), squamous cell carcinoma, and leiomyosarcoma; benign tumors such as leiomyoma and plasmacytoma occur less often.2 Metastatic tumors are three times more common than primary esophageal tumors and occur through local invasion from the stomach, thymus, thyroid, and heart base as well as from mammary adenocarcinoma and lymphoma.1 In dogs, the most common primary esophageal tumors are osteosarcoma and brosarcoma, particularly in areas where Spirocerca lupi is endemic (Africa, Asia, southeastern United States) because neoplastic transformation of S. lupi granulomas frequently occurs.3 In cats, the most common primary esophageal tumor is squamous cell carcinoma.4 Leiomyomas are benign tumors of smooth muscle origin arising in the gastrointestinal tract. The well-de ned, round-to-ovoid masses are thinly encapsulated and expansile, usually with no ulceration of the overlying mucosa.5 Most (80%) arise intramurally from the muscularis propria (deep muscular layer), with a smaller percentage being pedunculated and arising from the muscularis mucosae. Esophageal leiomyomas are usually individual, slow-growing tumors, although multiple tumors can occur. In dogs, leiomyomas are most commonly found in the stomach at the gastroesophageal junction, and incidence increases with age.5 In people, leiomyomas occur most frequently in the esophagus and account for two-thirds of all benign esophageal tumors.6 Histologically, leiomyomas are distinguished from leiomyosarcomas by having a lower number of mitotic gures as well as the absence of capsular invasion and necrosis.7,8 Low-grade leiomyosarcomas may behave similarly to leiomyomas in dogs after marginal excision (removal of the entire lesion and only a small margin of surrounding tissue).8 aspiration pneumonia. In some cases, respiratory signs may be the only signs.1,9 The history of dyspnea, coughing, and panting seen in this case is speculated to be due to minor episodes of aspiration secondary to dysphagia. Esophageal tumors smaller than 2 cm seldom produce clinical signs.10 Leiomyomas at the gastroesophageal junction can be an incidental nding in asymptomatic patients at necropsy.5 However, in one dog, an esophageal leiomyoma just proximal to the lower esophageal sphincter was associated with megaesophagus and hypomotility.9 Large intra-abdominal leiomyomas and leiomyosarcomas have been reported to cause hypoglycemia in dogs as a paraneoplastic syndrome, likely because of the production of insulinlike growth factors.11 In people with esophageal leiomyomas, 15% to 50% of patients are asymptomatic, with no direct correlation between tumor size and the severity of symptoms.6 Diagnosis Thoracic radiographs may reveal a homogeneous mass in the region of the esophagus, with gas retention and dilatation proximal to the lesion. The mass may also appear calci ed.1,6,9 A barium esophagogram typically reveals a rounded or lobulated, smoothly elevated Clinical signs Clinical signs of esophageal tumors are most commonly due to luminal obstruction or motility dysfunction causing regurgitation and dysphagia. Other signs include weight loss, pain, and 608 November 2008 VETERINARY MEDICINE

Table of Contents Feed for the Digital Edition of Veterinary Medicine - November 2008

Veterinary Medicine - November 2008 Contents Leading Off Editors' Guest Just Ask the Expert Letters Practice Makes Perfect Clinical Exposures Practice Matters Idea Exchange Author Guidelines A Challenging Case: Esophageal Leiomyoma in a Dog Osteoarthritis in Cats: What We Now Know About Recognition and Treatment Product Preview CE Form/Advertiser Index Marketplace/Classifieds Mind Over Miller

Veterinary Medicine - November 2008

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