Stomach cancer is uncommon in dogs, making up less than 1% of canine cancers.1,2 The most common type is adenocarcinoma (carcinoma), which usually affects dogs aged about 7 to 11 and is more common in breeds such as Belgian Shepherds, Chow Chows and rough Collies.1,2 The main signs are vomiting, sometimes with blood, poor appetite and weight loss, which overlap with many everyday stomach problems.1,2 Stomach adenocarcinoma has often spread by the time it's found. After surgery, median survival is about 6 months, longer when the tumor is fully removed; without treatment, most dogs live under 3 months.3,1,2 Smooth-muscle tumors and GIST do much better after surgery.1
See your vet promptly if your dog has:
- Vomiting that keeps coming back over days or weeks, especially with weight loss1,2
- Vomit containing blood1
- Pale gums, weakness or tiredness, which can mean blood loss from a bleeding tumor1
- A swollen or painful belly1
See also dog vomiting and vomiting blood.
What the Research Says
- Surgery outcomes are better than once thought. In a 2019 multicenter study of 40 dogs with stomach carcinoma, median survival after surgery was 178 days, longer than historically reported.3
- It runs in some families. A 2025 Dutch study estimated that about 4.7% of Tervuren and 2.1% of Groenendael Belgian Shepherds develop stomach carcinoma within 10 years, with a strong inherited component.4
- Endoscopy finds more tumors than ultrasound. In one series, ultrasound found abnormalities in only 50% of stomach tumors, compared with 95% for endoscopy.1
- Spread is common. Estimates of spread by the time of diagnosis or euthanasia range from about one-third to as high as 70% to 90%.1,2
Types of Stomach Tumors in Dogs
| Type | What to know |
|---|---|
| Adenocarcinoma | The most common; aggressive, usually in the lower part of the stomach near the outlet1,2 |
| Leiomyoma | A benign smooth-muscle tumor, usually in dogs 10 to 15 years old1 |
| Leiomyosarcoma and GIST | Malignant smooth-muscle and stromal tumors; often long survival after complete removal1 |
| Lymphoma | Treated mainly with chemotherapy; see lymphoma in dogs1 |
Signs of Stomach Cancer in Dogs
- Vomiting, with or without blood1,2
- Poor appetite and weight loss1,2
- Lethargy2,1
- Diarrhea1
- Anemia from a bleeding ulcerated tumor1
- Belly pain or fluid if the tumor has spread1
- Weakness or collapse from low blood sugar with some smooth-muscle tumors1
Early signs are mild or absent, and they overlap with inflammatory and other stomach problems, so persistent vomiting with weight loss needs a vet check.2,5 See also blood in dog stool.
Which Dogs Are at Risk?
Diagnosis
- Bloodwork can show anemia from blood loss.1
- Ultrasound is often the first imaging test and shows thickening and changes in the stomach wall layers.5,1
- Endoscopy (a camera passed into the stomach) finds more tumors and allows biopsies, though small samples can miss deeper tumors.1
- Surgical biopsy through the full stomach wall is more definitive.1
- CT helps with staging and surgical planning.5
Treatment
Surgery to remove the tumor and part of the stomach is the main treatment for adenocarcinoma, smooth-muscle tumors and GIST that haven't spread.1,2 Surgery near the stomach outlet can require complex reconstruction. Risks include leakage with infection in the belly (peritonitis), bleeding, pancreatitis and clotting problems. In the 2019 study, 8 of 40 dogs had major complications.1,3
Chemotherapy is the main treatment for stomach lymphoma.1 For adenocarcinoma, effective chemotherapy hasn't been established, although one study linked it to longer survival after surgery.1,3,2 A targeted kinase-inhibitor tablet may be used for GIST that can't be removed.1 Anti-nausea medicine, appetite support and pain control help keep dogs comfortable.6
Life Expectancy
| Tumor type and treatment | Typical survival |
|---|---|
| Adenocarcinoma, no treatment | Usually under 3 months after signs begin2 |
| Adenocarcinoma, after surgery | Median about 6 months (178 days), longer with complete removal3,1,2 |
| Leiomyosarcoma or GIST anywhere in the gut, complete removal | Median about 3.5 years (42 months)1 |
| Leiomyoma | Benign1 |
Your vet or oncologist can estimate your dog's outlook based on the tumor type and stage.
Frequently Asked Questions
What are the signs of stomach cancer in dogs?
Vomiting, sometimes with blood, poor appetite, weight loss and lethargy.
Which breeds get stomach cancer?
Belgian Shepherds, Norwegian Lundehunds, Chow Chows, rough Collies, Staffordshire terriers and standard Poodles.
How long can a dog live with stomach cancer?
Without treatment, usually under 3 months. After surgery for adenocarcinoma, about 6 months on average; smooth-muscle tumors often do much better.
How is stomach cancer diagnosed in dogs?
With ultrasound and endoscopy, and a biopsy to confirm the tumor type.
Is stomach cancer painful for dogs?
It can cause nausea and belly discomfort, especially as it advances. Ask your vet about pain and anti-nausea medicines.
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Sources and further reading
This article was rewritten and fact-checked on October 28, 2026 against current veterinary references and specialist guidelines:
- Matsuyama A. Gastrointestinal Neoplasia in Dogs and Cats. Merck Veterinary Manual (professional version), full review January 2025.
- Araújo D, Cabral I, Vale N, Amorim I. Canine gastric cancer: current treatment approaches. Veterinary Sciences 2022;9(8):383.
- Abrams B, Wavreille VA, Husbands BD, et al. Perioperative complications and outcome after surgery for treatment of gastric carcinoma in dogs: a Veterinary Society of Surgical Oncology retrospective study of 40 cases (2004-2018). Veterinary Surgery 2019;48(6):923-932.
- Hugen S, Limpens C, Robben JH, Fieten H, Mandigers PJJ. Incidence and heritability of gastric carcinoma in the Belgian Shepherd dog population in the Netherlands. Veterinary Sciences 2025;12(1):18.
- Agut Giménez A. Imaging gastrointestinal tumours in dogs and cats. SEVC Annual Conference, Barcelona, 2017 (hosted by IVIS).
- Murgia D. Managing oncology patients: hospice and palliative care. Vet Times, November 14, 2023.
About this article
Last updated : fully rewritten using the Merck Veterinary Manual, a 2019 multicenter surgical study, a 2022 review, a 2025 Dutch Belgian Shepherd study and IVIS-hosted proceedings; added the research summary, tumor types, breeds, diagnosis, treatment, survival table, key takeaways and FAQ.
This page is for general information and is not a substitute for an exam by your veterinarian.
