Causes of a Hard Lump in a Cat's Tail

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Your cat expresses their emotions through their tail. Just by looking at that appendage, you know if they're happy, annoyed, or frightened. However, your cat's tail can tell you something about your cat's health too, especially if the tail has been damaged. If your cat has a bump or small bumps on their tail that aren't usually there, observe them for symptoms that can give a clue to the nature of the injury and call your veterinarian.


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Beware of a broken cat tail

If your cat has a bump on their tail or a sharp bend, especially near the tip, it can mean that they broke it at one time. While you'd likely be aware of such an incident in a pet you had since kittenhood, that might not be the case in a cat who came into your life when full grown. The lump forming after a fracture could have resulted because the cat continued to move their tail during the healing process.


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There's no real treatment for minor tail fractures — generally, they heal on their own. However, more serious tail fractures can sometimes require amputation.

Consider a feline cyst or tumor

A painful lump or lesion at the base of a cat's tail could be a tumor, either benign or malignant. Your veterinarian can't tell whether or not a tumor is potentially deadly by simply looking at it, so they'll either remove the entire tumor if it's small or take a sample from a larger tumor and send specimens for testing — a process called a biopsy. But before doing a biopsy, samples from a large (or even small) tumor are usually first retrieved via fine needle aspiration, which doesn't require anesthesia.


If the tumor is benign, no further treatment is necessary unless it's a sebaceous cyst. That's an encapsulated tumor filled with sebum — an oily substance produced by the skin's sebaceous glands — which your veterinarian can surgically remove. If a tail tumor does turn out to be cancer, your veterinarian might recommend tail amputation for the sake of your cat's wellness.


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Understand cat tail abscesses

A large, painful swelling on your cat's tail could indicate an abscess in the affected area. Outdoor tomcats are most likely to suffer from tail abscesses and skin infections since most abscesses result from fighting. The tail area is a common site for bites, as the dominant tomcat might inflict a bite as the other cat flees.


Bacteria from a bite cause the site to fill with pus. Within a few days, you'll notice hair loss around the swelling. If your cat hasn't already gone to the veterinarian to have the abscess lanced, it could break at home, releasing large amounts of blood and pus. However, even if the tail injury ruptures on its own, you should still take your cat to the veterinarian. Other punctures might be present on the cat's body but not readily visible. These wounds still need to be clipped and cleaned with topical antiseptics.



Your veterinarian will prescribe antibiotics to combat infection. Large abscesses could require the veterinarian or veterinary technician to drain them. Additionally, pet parents might hear that their cat might need a Penrose drain, which is a piece of plastic tubing surgically added to the wound to prevent it from closing prematurely.


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Overactive male cat glands and stud tail

Although tomcats primarily develop stud tail — hence the name — neutered males and spayed females might also come down with this malady. Although male cats might mark territory often by repeatedly rubbing objects with a gland located at the base of the tail, that's not what causes gland overactivity.


Overactivity of the gland is technically known as supracaudal gland hyperplasia. The gland is overactive because male hormones cause more sebum to secrete — unneutered males produce more male hormones. A stud tail results when hair follicles are blocked by the overproduction of sebum. The blocked follicles can cause raised bumps on the cat's skin (sometimes called feline acne), matted hair, and bacterial skin infections that can impact your cat's health.

Your veterinarian will clip off the matted hair and recommend a degreasing shampoo to get rid of the excess oil caused by sebaceous gland overactivity. If an infection exists, they might prescribe antibiotics. If your cat isn't neutered, your veterinarian will likely recommend that surgery too.

The bottom line

There are several reasons a cat might have a lump on their tail, but the most common are a breakage, an abscess, cysts, or a tumor. A lump or bend in the tail might result from a break that healed incorrectly. A skin lump could also be a tumor that needs to be tested by a veterinarian for possible cancer. An abscess or cyst likely requires drainage and a prescription for an antibiotic from your DVM to improve your pet's health.


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