What That New Lump on Your Dog Might Be (And Why You Shouldn’t Ignore It)
- Dr. Liz Munro
- Aug 11
- 5 min read
Finding a lump on your dog can be alarming. Whether it’s a soft swelling under the skin or a firmer, more visible bump, your first instinct may be concern—especially if your dog is getting older. The truth is, while many lumps in dogs are completely harmless, others can signal a more serious issue. The key is not to ignore them.
In this guide, we explore the range of possible causes behind new lumps, explain what changes to look for, and highlight why early veterinary checks are essential for peace of mind and good outcomes.
Contents
Common Causes of Lumps in Dogs
Dogs develop lumps for a variety of reasons—some completely benign, others requiring closer monitoring or treatment. These growths can appear at any age but are especially common in middle-aged and senior dogs. They may grow slowly, remain unchanged, or change suddenly.
Some of the most frequent types include:
Lipomas (fatty lumps): These are among the most common benign lumps in dogs. Soft, round, and moveable under the skin, they typically grow slowly and are most often found on the chest, belly, or thighs. They’re usually painless, though large ones can interfere with movement.
Sebaceous cysts: These blocked oil glands form small, dome-shaped lumps that may rupture or leak a thick white or yellowish substance. While generally harmless, they can become infected or irritated.
Abscesses: Caused by infection, often following a bite or scratch, abscesses are painful swellings filled with pus. They may feel warm to the touch and require prompt drainage and antibiotics.
Warts (papillomas): Typically seen in younger dogs or those with compromised immune systems, these small cauliflower-like growths are caused by a virus. They usually appear on the lips, face, or inside the mouth and may go away on their own.
Skin tags: These small, hanging growths are generally harmless but may become snagged or bleed. Dogs can develop more with age.
Mast cell tumours: These are unpredictable and potentially cancerous. They can resemble benign lumps but may change size and texture or become ulcerated. Immediate assessment is essential.
Soft tissue sarcomas: A group of malignant tumours that originate in connective tissue. They are often firm, poorly defined, and can invade surrounding tissues if left untreated.
Mammary tumours: Seen mostly in unspayed female dogs, these lumps can range from benign to malignant and are typically found along the belly or near the teats.
Because many types of lumps look similar, the only way to know for certain what you’re dealing with is through diagnostic testing.
Signs That Warrant Prompt Attention
While it’s tempting to take a “wait and see” approach, there are some characteristics that suggest a lump needs urgent evaluation. Some changes are obvious, like rapid growth, but others can be more subtle.
Keep in mind that not all dangerous lumps are painful or dramatic—some of the most serious begin as small, unremarkable bumps. It’s also possible for previously benign lumps to change over time.
Be especially alert if a lump is:
Growing quickly: Rapid enlargement can indicate inflammation, infection, or malignancy and shouldn’t be ignored.
Firm or immovable: Lumps fixed to deeper tissue layers are more concerning than soft, freely moveable ones.
Ulcerated, red, or bleeding: This may indicate trauma, infection, or a malignant tumour like a mast cell tumour.
Painful or sensitive: If your dog winces when touched, there may be inflammation or infection involved.
Causing irritation: Lumps that prompt licking, biting, or scratching can quickly worsen or become infected.
Affecting movement: Lumps near joints or on limbs may limit your dog’s ability to walk, run, or lie down comfortably.
Accompanied by systemic signs: Such as lethargy, reduced appetite, vomiting, or unexplained weight loss—these may point to internal illness.
All new lumps should be checked by a Vet, and this should be repeated if the lump subsequently changes, and also at any routine health checks.
Why Early Checks Matter
Early detection of any abnormality dramatically improves your dog’s chance of a positive outcome. A lump doesn’t need to be large or painful to pose a risk. Many cancerous tumours can look deceptively minor in their early stages, and delaying assessment may limit treatment options or allow conditions to progress unnecessarily.
Timely vet visits can make all the difference:
Less invasive treatment: Small, early-detected lumps can often be removed with minimal surgery, reducing stress and recovery time.
Better prognosis: Malignant lumps caught early are more likely to be fully removed before they spread.
Monitoring opportunities: Your vet can measure and track benign lumps over time, so any changes are quickly noticed.
Comfort for your pet: Even harmless lumps can cause discomfort if they grow large or interfere with movement or grooming.
Routine checks during grooming or cuddle sessions are one of the best ways to notice new lumps. Be thorough—feel around the legs, chest, armpits, and belly, where growths often go unnoticed.
What to Expect at a Vet Appointment
If you find a new lump, don’t panic. Most vets will start with a calm, methodical assessment, asking when you first noticed the lump and whether it has changed in size, colour, or texture.
They’ll also perform a hands-on examination to determine consistency, depth, and mobility.
Further diagnostics may include:
Fine needle aspiration (FNA): A quick procedure where a thin needle extracts cells for lab analysis. It’s minimally invasive and often done during the initial consult.
Biopsy: Involves removing part or all of the lump under sedation or anaesthesia, especially if the sample from an FNA is inconclusive.
Imaging (X-rays, ultrasound): Used to check for deeper masses or to assess if a suspicious lump has spread internally.
Blood tests: To assess your dog’s general health and check for signs of systemic illness before any surgery.
With the results, your vet will advise on whether the lump needs removal, monitoring, or treatment—and help you make an informed decision for your pet.
FAQs
My dog’s lump isn’t changing—do I still need to check it?
Yes. Even stable lumps should be examined to confirm they’re benign. Monitoring is only safe when a proper diagnosis has been made.
Do dogs get more lumps as they get older?
Yes. Senior dogs are especially prone to benign fatty lumps and skin growths. However, age also increases the risk of certain cancers, so continued vigilance is important.
Can I prevent my dog from developing lumps?
Not always. While a healthy diet and regular check-ups help overall wellness, many lumps occur due to genetics, age, or chance. Early detection is your best defence.
Should I remove a lump just in case?
Not necessarily. Some benign lumps don’t need removal unless they’re causing discomfort or interfering with your dog’s daily life. Your vet will guide you based on the location, type, and risk level of the lump.
