My dog has a lump on his tail and keeps biting it. What is it?
Updated On September 23rd, 2025
Pet's info: Dog | Mixed Breed Medium (23 - 60lb) | Male | neutered | 45 lbs
my dog has a big lump on his tail but I don’t know if it’s a tumor or something bad or it’s because he bites his tail quite frequently but regardless of what it is I need help
2 Answers
Most Helpful Answer
Published on September 25th, 2023
Thank you for contacting Petco Pet Education Center, formerly Petcoach with your question about Toby and for providing a picture of his lump, it's very helpful. That is quite a big lump, and he will be biting his tail because it's bothering him. This lump could be a cyst, abscess, a benign tumor, or a malignant tumor. Unfortunately I cannot diagnose what it is without seeing him in person. Any suspicious lumps should be examined by the vet. The vet can perform a test called a fine needle aspirate on it. To do this, the vet sticks a small needle into the lump to get a sample of its cells, and examines the cells on a slide under a microscope. It's usually painless to the animal, and relatively quick to perform. Once the cause of the lump is diagnosed, the vet can discuss treatment options if needed. Give his vet a call now to make him an appointment. Until he sees the vet, I would put an Ecollar on him to keep him from biting his tail further. If you don't have one at home already, you can buy one at a pet store. I hope this helps!
7Pet Parents found this answer helpful
Related Answers from Veterinarians
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Published on November 15th, 2016
The black bump could be trauma from chewing on his tail (which is a sign of itchiness), or it could be a tumor (benign or malignant). I would take Bentley into the vet for an exam. The vet can determine if the bump is caused by constantly chewing on his tail, or if it is caused by something else. To check to see if it a tumor, the vet can perform a fine needle aspirate on it. To do this, the vet sticks a small needle into the lump to get a sample of it's cells, and examines the cells on a slide under a microscope. It's usually painless to the animal, and relatively quick to perform. I would take Bentley into the vet tomorrow for an exam.
1Pet Parents found this answer helpful
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