Clinical and histopathological characteristics of two canine gastric vascular hamartomas

Canine gastrointestinal hamartomas are rare presentations that have only been detected once with a gastric location, in a case of smooth muscle hamartoma [1]. Like other diseases causing an encumbrance on the gastric lumen, they can clinically manifest with gastrointestinal signs [2]. Two elderly mixed breed dogs presented with chronic vomit and lack of appetite, with ultrasound and tomographic evidence of an intraluminal gastric mass of unknown origin. In both cases, the masses were surgically resected and sent to the histopathology service of the Department of Comparative Biomedicine and Food Science. The two masses appeared macroscopically as either an exophytic mucosal and submucosal polypoid proliferation affecting the fundic region (dog 1), or as a mural submucosal bulging mass from the pyloric region (dog 2). After fixation and processing, the histological slides were evaluated by hematoxylin-eosin (HE) staining. Sub-grossly, the polypoid mass (dog 1) was poorly demarcated, in contrast to the mass of dog 2. Microscopically, both showed an irregular proliferation of vascular structures considered veins and arteries, severely expanding the submucosa in both cases and displacing the tunica muscularis in one case (dog 2). The vessels were lined by factor VIII+ non-atypical endothelial cells, often supported by irregularly thickened and shaped, muscular, α-SMA+ walls. The vessels were often engorged by red blood cells and multiple intravascular thrombi were noted. The polypoid mass also showed a mild lymphocytic infiltration of the adjacent mucosa and submucosa, while the second mass had a necrotic center with dystrophic mineralization and neutrophilic inflammation. They have been diagnosed as a gastric hamartomatous polyp of vascular type (dog 1) and as a gastric vascular hamartoma (dog 2). Both dogs recovered well and were healthy one year after the surgery. Dog 1 is still alive, while dog 2 was euthanized for unrelated causes. In both cases, complete surgical excision was conclusive for diagnosis and treatment. This approach is indeed preferred to endoscopic biopsy, allowing the evaluation of the deeper layers. In conclusion, the two masses had a different macroscopic presentation that initially led to consider them two different entities. However, on microscopic examination, both showed a prominent proliferation of well-developed, but disorganized, non-infiltrating vascular structures characterized by strong immunolabeling for factor VIII and α-SMA protein. These findings led to a common diagnosis of gastric vascular hamartoma. Due to their good prognosis, hamartomas should be considered among the differential diagnoses and differentiated from neoplasms with which they can share the macroscopic presentation. [1] Taulescu et al. Gastric smooth muscle hamartomas mimicking polyps in a dog: A case description and a review of the literature. Case Rep. Vet. Med., 2013: 1–5, 2013. [2] Diana A, Penninck DG, Keating JH. Ultrasonographic appearance of canine gastric polyps. Vet. Radiol. Ultrasound, 50: 201-204, 2009.