Veterinary Society of
Surgical Oncology

BIOLOGIC BEHAVIOUR

General Considerations

  • gastric tumors are uncommon and account for < 1% of all cancers
  • etiology unknown although chronic nitrosamines administration may cause gastric carcinoma in dogs

Gastric Carcinoma

  • gastric ADC is rare in cats but accounts for 42%-72% of all canine gastric tumors
  • mean age 8 years, but 19% dogs are < 5 years
  • sex predisposition: male with a male-to-female ratio of 2.5:1
  • breed predisposition: Belgian Shepherd and Rough-Coated Collie
  • location: pyloric antrum or lesser curvature
  • 3 anatomic descriptions:
  • scirrhous due to firm and non-distensible texture = linitis plastica
  • plaque-like mucosal lesion with large central ulcer
  • raised polypoid lesions
  • metastatic rate 74% in dogs with sites including gastric lymph node, peritoneum, liver, lungs, omentum, adrenal glands, duodenum, pancreas, spleen, esophagus, kidneys, diaphragm, myocardium, long bones, pituitary gland, bile duct, brain, and testes

Lymphosarcoma

  • LSA is the most common gastric tumor in cats (solitary or multicentric) and most are FeLV negative
  • sex predisposition: males
  • gross appearance: discrete mass or diffuse gastric wall diffusion

Leiomyoma

  • leiomyoma is common in very old dogs and is the 2nd most common gastric tumor in dogs
  • mean age 15 years with 82% prevalence in 17-18-year-old Beagles
  • discrete solitary lesions (usually pedunculated) in the cardia or gastroesophageal junction causing mass effect
  • ulceration is uncommon

Carcinoids

  • gastric carcinoids are tumors of the enterochromaffin system and are referred to as amine precursor uptake and decarboxylation tumors or APUDomas
  • gastric carcinoids are functional and, in humans, are diagnosed by clinical presentation, measurement of urinary serotonin metabolites, provocative pentagastric testing, radionucleide scans, and CT
  • carcinoids are locally invasive, and metastasize to regional lymph nodes, lungs, pleura, and peritoneum
  • carcinoids usually occur in geriatric animals and gastric carcinoid has been reported in a 15-year-old cat

Other

  • other malignant gastric tumors include FSA, leiomyosarcoma, plasmacytoma, and carcinoid
  • metastasis to the liver and duodenum reported in both cases of leiomyosarcoma
  • benign gastric tumors include adenoma, leiomyoma, or hypertrophic gastropathy
  • adenomatous polyps are usually an incidental finding but they may cause pyloric obstruction

CLINICAL FEATURES

Clinical Signs

  • clinical signs are caused by gastric outflow obstruction, altered motility, or chronic blood loss secondary to tumor necrosis and ulceration
  • progressive vomiting is common and may contain fresh or digested blood
  • weight loss may be caused by poor digestion, protein malnutrition, or cancer cachexia

DIAGNOSIS

Laboratory Tests

  • laboratory tests and survey radiographs are usually unrewarding
  • leiomyoma and leiomyosarcoma have been associated with paraneoplastic hypoglycemia
  • microcytic hypochromic anemia is common with chronic blood loss and occult blood may be detected in feces
  • increased liver enzymes may be seen with hepatic metastasis or obstruction of the common bile duct

Imaging

Radiographs

  • positive- or double-contrast radiographs: gastric tumors can appear as a mass effect, ulcer crater, delayed gastric emptying with poor motility, and delayed adherence of contrast material to an ulcerated tumor

Ultrasonography

  • ultrasonographic findings include transmural thickening of the gastric wall with loss or altered layering (poor echogenic outer and inner lining with hyperechoic central zone)
  • other findings include tumor location, ulceration, extension through gastric wall, and lymphadenopathy
  • gastric ADC tend to appear as sessile mass located in the lesser curvature or antrum
  • benign lesions tend to be either pedunculated or well circumscribed with gastric leiomyoma commonly located in the cardia

Endoscopy

  • gastroscopy allows direct visualization and guided biopsy
  • several biopsies should be performed as superficial ulceration, necrosis, and inflammation is common
  • submucosal masses are difficult to biopsy and false-negative results are common

Other Imaging Techniques

  • CT and MRI

TREATMENT

Surgery

General Considerations

  • surgery is recommended for gastric ADC and possibly solitary feline gastric LSA but complicated by advanced stage at presentation, frequent metastasis, difficult access, and debilitated animal
  • lymph node metastasis is variable and all abdominal lymph node should be evaluated for staging purposes
  • curative resection should be attempted if disease is localized to the stomach
  • surgical techniques: Billroth I or II or palliative bypass procedures
  • Billroth I or II provides immediate relief of gastric outflow obstruction and clinical improvement in early postoperative period
  • Billroth II (partial gastrectomy and gastrojejunostomy) or complete gastrectomy (with biliary by-pass) are very extensive surgeries with high morbidity and minimal survival advantage
  • partial gastrectomy preferred in humans due to better nutritional status and quality of life and radical gastrectomy does not improve survival time
  • palliative gastrojejunostomy for inoperable or metastatic lesions but associated with significant morbidity including anastomotic ulcers

Leiomyoma

  • gastrotomy via exploratory ventral midline or lateral intercostal thoracotomy approach
  • gastrotomy and submucosal resection recommended with minimal risk of contamination, hemorrhage, or stricture, and good tumor control

Chemotherapy

  • no known effective chemotherapy agents for gastric ADC
  • gastric LSA does not respond well to conventional chemotherapy protocols and chemotherapy may not be required following surgical resection of solitary gastric LSA in cats

Prognosis

  • prognosis depends on surgical excision, tumor type and grade, and presence of metastatic lesions
  • prognosis is poor for gastric ADC as majority are dead within 6 months due to either recurrent or metastatic disease
  • gastric leiomyosarcoma: MST 12.0-21.3 months, with 1-year survival rate 75% and 2-year survival rate 66%
  • 54% metastatic rate, but metastasis is not a poor prognostic factor with a MST 21.7 months
  • gastric LSA: MST 40 weeks with Madison-Wisconsin protocol and 15.5 months with prednisolone-chlorambucil
  • benign lesions and extramedullary plasmacytoma have an excellent prognosis following surgical resection

GASTRIC TUMORS

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