As Amazon Associates, we may earn from qualifying purchases. See disclosure in sidebar.

Dog’s Tail with a New Lump: What Is It? [Pictures & Vet Advice]

Score for Seniors:
Activity Level:
Weight: Pounds

dog wagging tail

While I see dogs and their owners about new lumps and bumps most days, tail lumps are rather uncommon. Of course, they do occur, but they are quite infrequent when compared to lumps appearing on other parts of the body like the chest, limbs or abdomen.

Given how dogs wag their tail, it would not be uncommon for an owner to first notice a tail lump when it is banged against something and starts to bleed. This in itself is not a worry, as even benign lesions like warts can bleed when banged. In this article, we will review the top causes of tail lumps and bumps (with pictures), and what to do.

Tail lumps and bumps: top causes

1. The tail gland

Interestingly, the most common ‘tail lump’ an owner will present to me is not a tail lump at all! Indeed, the tail gland (supracaudal or ‘violet’ gland) is a normal part of the dog’s anatomy, but many owners become concerned when they see it for the first time.

patch of hair loss (tail gland bump)

Tail glands are flat and can become more bald and prominent with age, especially in males. Their job is to secrete oils. If the gland does swell up, this is known as ‘stud tail’. The excess sebum produced can make the area greasy and lumpy. We treat this by using medicated washes and some dogs would need antibiotics for any secondary infection.

2. Sebaceous cysts

Sebaceous cysts are usually small lumps that are a blue, grey or clear color. They tend to have a smooth surface. If the cyst bursts, the contents resemble cottage cheese. Once a dog develops one cyst, they tend to develop more as they get older.

sebaceous cyst on a dog's tail

If the cyst is small and not bothering the dog, it is often left alone. However, if it is continually becoming infected or if the vet is unsure what it is, it would be best removed.

3. Skin tags and warts

Skin tags and warts are incredibly common and many of our furry friends will develop them in their golden years. While the tail is not the typical place for them to occur, they can grow anywhere on the skin. These lesions tend to be small and not well attached to the skin. They can be a range of colors but many are flesh colored.

WATCH: 3 Important Tips To Care For an Old Dog [VET VIDEO]

wart on a Cocker Spaniel dog

Skin tags and warts are benign and are only removed if bothering the dog or if growing rapidly. As most patients who develop them are older, we’d usually only remove them surgically when medically necessary.

4. Cancers (such as mast cell tumors, sarcomas and sebaceous tumors)

Some tail lumps will be malignant, which is why it is so important to have new growths examined by a vet. As mentioned, tail cancers are very uncommon. I probably see just a handful of cases a year in my busy practice.

mast cell tumor on dog's leg

These cancers can be any of the same tumors that we see on the skin elsewhere on the body, such as mast cell tumors and soft tissue sarcomas.

With any cancerous lump or lesion, the key is in diagnosing and treating it early. The prognosis depends on the type and grade of cancer and whether or not it has already spread. For large and aggressive cancers, tail amputation may be the best way forward.

5. Cornifying epitheliomas

These are benign growths that stick up from the skin, almost like a horn. These funny looking growths tend to appear on the back or tail of the dog. They have quite a characteristic appearance so are quite easily diagnosed.

benign growth on a dog's tail

As with other benign skin lesions, we often just leave these growths alone but keep an eye out for any changes or infections. If the lesion is bothering the dog, it can be surgically removed.

When should you worry about a new tail lump?

Any new lump should be examined by a vet, particularly if it is bothering the dog or has been present for more than 1-2 weeks. Lumps that are rapidly growing, bleeding or infected should be examined promptly.

If you’ve just noticed a small lump and your dog is not rubbing or chewing at it, you may decide to monitor it for a week or two, to see if it resolves. Something like an insect bite may be gone within a few days, without any treatment.

What are other frequent issues with dog’s tails?

The tail is covered in skin and can develop any of the skin issues we see more commonly in other regions of the body. This includes allergic skin rashes, seborrhea and fur loss. Indeed, fur loss over the tail is not uncommon in hormonal disorders including hyperthyroidism, and we often refer to the bald tail as a ‘rat tail’.

Some dogs who wag their tail a lot can split the skin at the end. This can lead to bleeding and chronic infections. This sort of problem can be very tricky to deal with, but the aim is to secure the home so the tail is not banging off things like furniture and doors. Some dogs will need their tail bandaged for several days as it heals.

Disclaimer: This content is not a substitute for veterinary care. Always consult with your vet for health decisions. Learn more.

Cost of diagnosing a lump at the vet

When determining what sort of lump or bump we’re dealing with, your vet will first examine the tail and new lesion during a consultation. They’ll then decide if they think it is necessary to sample the lump.

A fine needle aspirate can be done to aspirate cells while the dog is awake, during a routine consult. The cells are sent to a laboratory for analysis and a report is received back within about 5 days. This procedure costs around $150-250.

A biopsy is when a larger sample of cells is taken, and this requires the dog to be sedated or anaesthetized. This procedure is more likely to provide a diagnosis and costs about $250-350 depending on how large the patient is.

Can a vet diagnose a lump through a video call (instead of an in-office appointment)?

Video call consults are convenient and a particularly good option for busy owners or nervous dogs. However, there are limitations.

I personally perform online consults and would feel comfortable diagnosing straightforward warts or cysts on the tail after seeing a photo or video. However, there will be lesions that need to be assessed in person and/or biopsied before we know what they are.


  • Dr. Linda Simon, Veterinarian

    Dr Linda Simon (MVB MRCVS) has 10 years of experience as a veterinarian. She is a veterinary surgeon with a special interest in geriatric patient care, dermatology and endocrinology. She is a member of the British Royal College of Veterinary Surgeons. She graduated top of her class from UCD School of Veterinary Medicine in Dublin in 2013. Linda has also worked as a locum vet in a range of clinics, including 24 hour emergency clinics and busy charity clinics.

Be the first to comment

Leave a Reply

Your email address will not be published.


This site uses Akismet to reduce spam. Learn how your comment data is processed.