Help! My Dog Has A Lump

‘At A Glance (Details Below)’ What to do

When A Dog Has A Lump

  1. Get new lumps checked regularly to ensure they are not cancerous
  2. Most lumps are benign and can be diagnosed on the spot at the vet
  3. Successful removal on the head, tail and legs requires earlier surgery

Now dive deeper…

If you’re a dog owner, it’s almost inevitable that you’ll find a lump at some point. Dogs get lots of lumps and bumps, especially as they get older. How do you tell which ones are more serious?

Believe me, it matters. You don’t want to know how often we see a lump that could have been removed if only the urgency had been recognised. The trick is to know the warning signs of dangerous lumps on dogs.

Which Dog Lumps Need Removal?

Some of the ways you can identify a dangerous lump are:

  1. Speed: if a lump looks bigger in only a month it’s growing rapidly
  2. Shape: smooth, round lumps whether on or under the skin are usually worse
  3. Appearance: black, pink or ulcerated surfaces are more worrying
  4. Feel: subcutaneous lumps should move easily between the skin and the body
  5. Position: watch out for lumps on the head, legs and tail (I’ll explain later)
Dog skin tumour
Typical appearance of many skin lumps such as mast cell tumours or histiocytomas. Slide shows typical FNA appearance


Later I’ll show you the most common lumps we see. However, the only way to know for sure is to take a biopsy. That’s where we take a small piece and get it examined. A biopsy does two important things:

  1. It tells us whether the lump is dangerous or not
  2. It helps us decide how big a surgical margin we need

Why Does Time Matter?

Keeping your options open is all about the margin. This is a rim of healthy tissue we cut around a mass to act as a quarantine zone. The size of the margin depends on the behaviour of the tumour.

  • If it sends out tendrils and satellites of tumour cells then the margin needs to be wide
  • If it tends to keep to itself, the margin can be narrow.

Let’s say we do a biopsy and find it’s a nasty tumour that needs a 2cm margin. Even if the lump is only 1cm wide, we have to cut a circle 5cm in diameter (and possibly 3cm deep) to get it out.

You can see the problem. There simply isn’t 5cm to remove on many legs, heads or tails. Even on the chest or abdomen, it’s not going to be easy.

Imagine what happens if people wait until the lump is 3cm. These dogs have no options left other than an amputation or reconstructive surgery if the lump is nasty.

Common Lumps Of Dogs

So the earlier we see a lump, the more options we have. If you’re afraid of bad news, don’t be; despite the horror stories, a biopsy or surgery isn’t always needed, and most lumps are benign. Your vet can even identify most lumps straight away. Here’s what they are and how we can tell.

Lipoma or Fatty Growth

What they are: the classic lump under the skin of older dogs. It’s actually a benign tumour of fat cells, and should grow so slowly it takes 6 months to see any change.

How we tell: a fine needle aspiration (FNA) like I’m demonstrating in the video gives a clear answer. Never assume a lump is a lipoma unless your vet has done this first.

Treatment: none, usually. Lipomas need removal only when they occur in difficult positions like the legs or armpits. I also take them off younger dogs if they will get huge in a normal lifespan.

Soft Tissue Sarcoma

What they are: fast-growing, locally invasive tumours of connective tissue, common in large breeds.

How we tell: biopsy is necessary. Sarcomas feel just like lipomas and are often mistaken for these if a needle aspirate isn’t done.

Treatment: prompt, careful resection with a wide margin.

Sebaceous Cyst

What they are: a blocked sebaceous gland causes a buildup of hard, cystic material under the skin.

How we tell: a fine needle aspiration gives a clear answer.

Treatment: none, usually. Most sebaceous cysts never cause problems.

Sebaceous Adenoma

sebaceous adenoma dogWhat they are: a benign tumour of sebaceous glands, often wrongly called a wart. Very common in Poodles, Maltese, Bichons and their crosses.

How we tell: biopsy is necessary, however, the classic appearance and slow growth make us near-certain just by looking.

Treatment: most sebaceous adenomas never cause problems, but any that are ulcerated or being licked need removal.

Skin Tag or Wart

canine papilloma
A wart: compare with sebaceous adenoma

What they are: multiple small lumps often on the face and head. Just like in humans, warts are caused by a papillomavirus; dogs that get them go to dog parks or day care.

How we tell: biopsy is necessary, however, their classic feathery appearance is hard to mistake.

Treatment: none. Although they can look terrible, warts should go away by themselves after a few months.

Mast Cell Tumour

What they are: fast-growing, pink button-like lumps which can be well-behaved or very aggressive. MCTs have a reputation for recurring following incomplete removal.

How we tell: your vet can usually do it via fine needle aspiration but sometimes a biopsy is required.

Treatment: should always be removed with a margin depending on the ‘grade’ or severity.

dog nasal infectionGranuloma

What they are: fast-growing, raised red lumps sometimes with a surface crust. Granulomas look like aggressive tumours but are actually a solid form of bacterial infection.

How we tell: sometimes a biopsy is required but we are often sure enough just from inspection.

Treatment: antibiotics, not surgery.


dog with melanomaWhat they are: slow-growing, dark lumps not caused by sunlight. Skin melanomas of dogs need removal, but they are a lot less malignant than human ones and shouldn’t make you lose sleep.

How we tell: there isn’t much else that’s black.

Treatment: removal. Baxter (pictured) gets repeated melanomas. After removing the first few we have been watching his latest set for signs of growth.

Haemangioma and Squamous Cell Carcinoma

What they are: two tumours caused by ultraviolet damage from sun exposure, common in Adelaide on pink hairless areas.

How we tell: haemangiomas are red, berry-like masses that bleed easily; squamous cell carcinomas are raised, crusty sores.

Treatment: removal. SCC, in particular, can spread to lymph nodes and cause death if left too long.

Phew! There are lots of rarer lumps on and under the skin but I hope you’ll never see them. For example, the other one at the start is a Sertoli Cell Tumour caused by a retained testicle. No dog should suffer from any of even the worst of these tumours if you get them checked in time.

Have something to add? Comments are welcome below and will appear within 24 hours of lodging.

By Andrew Spanner BVSc(Hons) MVetStud, a vet in Adelaide, Australia. These help topics are from a series regularly posted on Facebook and Twitter. The information provided here is not intended to be used as a substitute for going to the vet. If your pet is unwell, please seek veterinary attention.


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