# Lump on Your Dog's Side or Abdomen A lump on your dog's stomach is often a harmless skin growth, but it can also be a hernia or a mass inside the abdomen. The first step is figuring out whether the lump sits in the skin and fat layer or deeper, inside the belly. Where it sits changes what it might be and how quickly you need to act. This article is educational and is not a substitute for veterinary diagnosis or treatment. ## Quick Answer - Gently feel the lump. If you can pinch the skin and lift the lump away from the body wall, it is likely in the skin. If it feels fixed and deep, it may be inside the abdomen. - Skin tumors in dogs are very diverse and include harmless lumps, rashes, and nonhealing sores, so identifying them should be left to a veterinarian [1]. - A soft, squishy swelling that disappears when your dog lies down or pushes back in when pressed may be a hernia, which needs a vet visit. - A firm mass deep in the belly, especially with vomiting, not eating, or a swollen abdomen, needs same-day or emergency care. - Do not squeeze, poke, or try to drain any lump. Take a photo, note the size, and book an exam. ## What a Lump on the Belly Wall Looks Like and What Is Normal Dogs get lumps. Most older dogs have a few, and many are harmless. The belly and chest wall are common places for skin growths because there is a lot of skin and fatty tissue there. Normal findings include small, soft, movable lumps under the skin that have been there for months and have not changed. A lipoma is the classic example. It is a benign fat tumor, feels soft and squishy, and moves freely under the skin. A lump that is new, growing, firm, fixed in place, painful, or changing color is not normal. Tumors can appear as small bumps, but they can also look like hairless patches, rashes, or sores that will not heal [1]. Because skin tumors are so varied, only a veterinarian can tell them apart [1]. The tricky part is location. A lump you feel on the belly could be: - In the skin itself - In the fat layer just under the skin - In the abdominal wall muscle - Inside the abdomen, pushing outward The last one is the one owners miss. A mass deep in the belly can feel like a lump on the side of the stomach when you press. ## Common Causes of a Lump on the Side or Stomach Here is a simple table to help you think about what you are feeling. This is a guide, not a diagnosis. | Cause | Typical clues | How urgent | |---|---|---| | Skin tumor (benign or malignant) | In the skin, movable, may be hairless or ulcerated | Routine to urgent depending on growth | | Lipoma | Soft, squishy, movable, slow growing | Routine | | Hernia | Soft swelling that changes with position, may feel a hole | Same-day to urgent | | Abscess or infected pocket | Warm, painful, may drain fluid | Same-day | | Panniculitis (inflamed fat) | Multiple deep nodules, often with fever | Same-day | | Liver mass | Deep in the belly, may cause weakness or collapse | Urgent to emergency | | Splenic or mesenteric mass | Deep, may cause vomiting or a swollen belly | Urgent to emergency | ### Skin Growths Skin tumors are the most common reason for a lump on the belly. They range from harmless warts and cysts to malignant tumors. Some grow fast. A Merkel cell carcinoma, a rare malignant skin tumor, was reported in a 5-month-old puppy as a solitary, rapidly growing mass on the chest wall [2]. That case shows that even young dogs can get serious skin tumors, and that complete surgical removal can lead to a good outcome [2]. If you want more detail on telling skin lumps apart, see [Dog Skin Bumps and Lumps: When to See the Vet](/knowledge/veterinary-medicine/vet-visit-decisions/dog-skin-bumps-lumps) and [Why Is My Dog having lumps on skin? Lipoma vs Mast Cell vs Cyst Diagnosis](/knowledge/veterinary-medicine/symptom-guides/why-is-my-dog-having-lumps-on-skin-lipoma-vs-mast-cell-vs-cyst-diagnosis). ### Hernias A hernia happens when tissue pushes through a weak spot in the abdominal wall. It often feels like a soft, squishy lump near the belly button or along the groin. It may get bigger when your dog coughs or strains and smaller when they relax. Some hernias are harmless for years. Others can trap intestine, which is a surgical emergency. Only a vet can tell the difference. ### Panniculitis Panniculitis is inflammation of the fat layer. A 12-year-old dog was referred for a recurring fever and a palpable abdominal mass [3]. Imaging showed a mass and multiple deep subcutaneous nodules with mixed fluid and fat centers [3]. Surgery and biopsy showed sterile panniculitis, which was treated with long-term glucocorticoids [3]. This is a good example of a lump that looks scary but is not cancer. ### Liver and Abdominal Masses A mass in the liver can cause a lump you feel on the right side of the abdomen. One 7-year-old dog had a large mass on the right liver lobe and severe hypoglycemia, with blood glucose of 26 mg/dL [4]. The mass was removed, and the low blood sugar resolved [4]. Another dog had a liver nodule found on routine ultrasound, later diagnosed as hepatocellular carcinoma [5]. A mass in the spleen or the tissue around the intestines can cause a lump on the left side or center of the belly. One dog developed multiple mesenteric masses after a prior splenectomy, and biopsy showed benign ectopic splenic tissue, not cancer [6]. This shows that even large, irregular abdominal masses can be benign [6]. ### A Note on Imaging Ultrasound is a useful first step for looking at the liver and spleen, but it has limits. A review of 12 studies found that ultrasound alone often cannot tell benign from malignant changes, and false negatives happen even when organs look normal [7]. Definitive diagnosis usually needs cytology or histopathology, which means a sample of cells or tissue [7]. ## Red Flags That Make It an Emergency Call an emergency clinic now if you see any of these: - A firm, deep lump that appeared suddenly - A swollen, tight, painful abdomen - Repeated vomiting or retching - Pale gums, weakness, or collapse - Trouble breathing - A lump that is hot, red, draining pus, or bleeding - A hernia that is hard, painful, or cannot be pushed back - Sudden weakness or collapse in a dog with a known liver mass A swollen, painful belly can signal internal bleeding or a twisted organ. Do not wait to see if it improves. For more on this, read [Dog Swollen Stomach Pain](/knowledge/veterinary-medicine/veterinary-technology/dog-swollen-stomach-pain) and [Dog Swollen Stomach Symptoms](/knowledge/veterinary-medicine/symptom-guides/dog-swollen-stomach-symptoms). ## Safe Things You Can Do at Home While You Wait You cannot diagnose the lump at home, but you can gather useful information. - Measure the lump with a soft tape or compare it to a coin. Write down the size and the date. - Take clear photos from two angles in good light. - Note whether it is in the skin or deep. Try to lift the skin around it. - Check for pain. Does your dog flinch when you touch it? - Watch for changes in appetite, energy, vomiting, or stool. - Do not squeeze, puncture, or apply heat or ice to the lump. - Do not give any medication without asking your vet. Some common pain meds are toxic to dogs. If your dog seems comfortable and the lump is small and stable, a routine visit within a few days is reasonable. If anything changes, call sooner. ## What Your Veterinarian Will Check and Test Your vet will start with a physical exam. They will feel the lump and decide whether it is in the skin, the body wall, or deeper. They may ask you to stand your dog and watch the lump as your dog breathes. Next steps may include: - Fine needle aspirate. A small needle collects cells from the lump. This is quick and often done in the exam room. - Biopsy. A piece of tissue is sent to a lab. This gives a definitive diagnosis. - Ultrasound. This looks at organs inside the abdomen, including the liver and spleen. - X-rays. These can show large masses or fluid in the belly. - Blood work. This checks organ function and can reveal problems like low blood sugar. - CT scan. This gives detailed images and can find nodules you cannot feel [3]. Treatment depends on what is found. For most tumors, surgical removal is the most effective option, and it is often the least costly with the fewest side effects [1]. If malignancy is suspected, the vet will remove tissue around the tumor to get clean margins [1]. For tumors that cannot be fully removed, partial removal may still help, and radiation or chemotherapy may be used [1]. If the lump is a hernia, surgery may be recommended, especially if it is large or changing. If it is panniculitis, treatment may involve glucocorticoids, with the dose set by your veterinarian based on your dog's weight and response [3]. ## Prevention and Monitoring You cannot prevent most lumps. You can catch them early. - Do a monthly lump check. Run your hands over your dog's whole body, including the belly, chest, legs, and tail base. - Keep a simple log. Note the date, location, and size of each lump. - Watch for change. Growth, color change, or new pain matters. - Keep routine vet visits. Many masses are found during routine exams before owners notice them [5]. - If your dog had a splenectomy or prior abdominal surgery, tell your vet about any new lumps. Benign ectopic splenic tissue can mimic cancer on imaging in dogs with that history [6]. ## Limitations and When to Contact a Veterinarian This article cannot tell you what your dog's lump is. Only a veterinarian can do that after an exam and testing. Contact your vet the same day if: - The lump is new and firm - The lump is growing quickly - Your dog has mild vomiting or a mild decrease in appetite - The lump is painful or warm Go to an emergency clinic now if: - Your dog collapses, has pale gums, or struggles to breathe - The abdomen is swollen and painful - There is repeated vomiting or retching - A hernia is hard and cannot be reduced - There is heavy bleeding from the lump Schedule a routine visit if the lump is small, soft, movable, and unchanged for weeks. Even then, a vet should look at it. Skin tumors are too diverse to judge by feel alone [1]. ## Frequently Asked Questions ### Can a lump on my dog's stomach be harmless? Yes. Many lumps on the belly are benign, such as lipomas and cysts. Others are inflamed fat nodules that look serious on imaging but are not cancer [3]. Because harmless and harmful lumps can feel the same, a vet exam is the only way to know. ### Is a lump on the left side of my dog's abdomen more dangerous than one on the right? Not necessarily. Side alone does not tell you much. A mass on the left may involve the spleen or mesentery, while a mass on the right may involve the liver. Both can be benign or malignant, so testing matters more than location. ### How fast can a malignant lump grow? Some grow very fast. A Merkel cell carcinoma in a puppy was described as a rapidly growing mass on the chest wall [2]. If a lump doubles in size in days or weeks, call your vet right away. ### Will my vet always do surgery? No. Surgery is the most effective option for most tumors, but it is not always needed or possible [1]. Some lumps are monitored. Others are treated with medication. For tumors that cannot be fully removed, partial removal, radiation, or chemotherapy may be options [1]. ### Can ultrasound tell if the lump is cancer? Not on its own. A review of 12 studies found ultrasound has limited diagnostic certainty for liver and spleen masses and can miss disease even when organs look normal [7]. A definitive diagnosis usually requires cytology or histopathology [7]. ## Related Articles - [Dog Skin Bumps and Lumps: When to See the Vet](/knowledge/veterinary-medicine/vet-visit-decisions/dog-skin-bumps-lumps) - [Why Is My Dog having lumps on skin? Lipoma vs Mast Cell vs Cyst Diagnosis](/knowledge/veterinary-medicine/symptom-guides/why-is-my-dog-having-lumps-on-skin-lipoma-vs-mast-cell-vs-cyst-diagnosis) - [Dog Swollen Stomach Pain](/knowledge/veterinary-medicine/veterinary-technology/dog-swollen-stomach-pain) - [Dog Skin Tag or Tumor? How to Tell and What to Do](/knowledge/veterinary-medicine/skin-allergy-and-ear-care/dog-skin-tag-or-tumor) - [Dog Swollen Stomach Symptoms](/knowledge/veterinary-medicine/symptom-guides/dog-swollen-stomach-symptoms) - [Lump Under Dogs Skin: Comprehensive Veterinary Reference Guide](/knowledge/veterinary-medicine/oncology/lump-under-dogs-skin) - [Bump on Your Dog's Belly or Stomach: Causes and Next Steps](/knowledge/veterinary-medicine/skin-allergy-and-ear-care/dog-bump-on-belly) - [Lump on Your Dog's Rib Cage: What It Could Be](/knowledge/veterinary-medicine/symptom-guides/dog-rib-cage-lump) - [Fatty Lump or Tumor? Lumps and Weight Loss in Dogs](/knowledge/veterinary-medicine/skin-allergy-and-ear-care/dog-fatty-lump-vs-tumor) ## References 1. [Tumors of the Skin in Dogs - Dog Owners](https://www.merckvetmanual.com/dog-owners/skin-disorders-of-dogs/tumors-of-the-skin-in-dogs). Merck Veterinary Manual. 2. [Diagnosis and treatment of Merkel cell carcinoma in a puppy: A comparative oncology approach](https://pubmed.ncbi.nlm.nih.gov/42266333/). The Canadian veterinary journal = La revue veterinaire canadienne, 2026. 3. [Systemic sterile nodular panniculitis associated with an intra-abdominal mass in a dog](https://pubmed.ncbi.nlm.nih.gov/42699830/). The Canadian veterinary journal = La revue veterinaire canadienne, 2026. 4. [Resolution of Recurrent Severe Hypoglycemia After Surgical Excision of a Primary Hepatic Neoplasm of Uncertain Histogenesis in a Dog: A Case Report](https://pubmed.ncbi.nlm.nih.gov/42655842/). Veterinary sciences, 2026. 5. [Case Report: Contrast-enhanced US and CT imaging features of nodule-in-nodule hepatocellular carcinoma in a dog](https://pubmed.ncbi.nlm.nih.gov/42146040/). Frontiers in veterinary science, 2026. 6. [Ectopic Splenic Tissue Mimicking Malignant Neoplasia in a Dog](https://pubmed.ncbi.nlm.nih.gov/42433008/). Veterinary radiology & ultrasound : the official journal of the American College of Veterinary Radiology and the International Veterinary Radiology Association, 2026. 7. [Accuracy of ultrasound detecting splenic and hepatic round cell neoplasia in dogs compared to cytology and histopathology](https://pubmed.ncbi.nlm.nih.gov/42006388/). Veterinary evidence, 2025. ## Further Reading - [Merck Veterinary Manual: Dog Owners](https://www.merckvetmanual.com/dog-owners) - [Cornell Richard P. Riney Canine Health Center: Canine Health Information](https://www.vet.cornell.edu/departments-centers-and-institutes/riney-canine-health-center/canine-health-information) - [American Veterinary Medical Association: Pet Care](https://www.avma.org/resources-tools/pet-owners/petcare)