Canine gastric mucosal sarcoma: a novel tumour type

Gastric neoplasia is uncommon in dogs accounting for ⟨1% of all neoplasms. Mesenchymal tumours arise from the muscularis layer of the gastric wall and represent 10-30% of canine gastric neoplasms. Gastric sarcomas arising from the muscularis layer of the stomach have not previously been reported.

A 7-year-old, female spayed labrador was referred for investigation of chronic vomiting and regenerative anaemia. Abdominal imaging revealed a large solitary pedunculated mass (65 × 62 × 56 mm) within the pylorus and proximal duodenum. A Billroth I procedure was performed to resect the mass. Histopathology and immunohistochemistry were consistent with chronic hypertrophic pyloric gastropathy with atypical spindle cell proliferation confined to the mucosa. A Billroth II procedure was performed 5.5 months later due to local recurrence. A new omental nodule (12 × 13 mm) was identified 10 weeks later, which was surgically resected and confirmed a diagnosis of metastatic sarcoma. Adjuvant chemotherapy with doxorubicin was commenced. Repeat staging identified metastases to the pancreas and local tumour recurrence. The dog was euthanised due to clinical deterioration and biliary obstruction 20 months after the onset of clinical signs (14.5 months post Billroth I).

This is the first report of a gastric mucosal sarcoma in a dog. Distinct from primary gastrointestinal sarcoma, which arises within the muscularis, the mass was confined within the gastric mucosal layer. The pedunculated nature of this mass made it amenable to surgical resection, but ultimately local recurrence was identified along with metastases. Pancreatic metastases have not previously been reported in gastrointestinal sarcomas.