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What is this hard, bruised lump on my dog's back that's growing?

Updated on September 23rd, 2025

Pet's info: Dog | Mixed Breed Small (up to 22lb) | Female | spayed | 15 lbs

I have an 11 year old shih tzu maltese. She's had this hard lump on her back for a while now, probably over a year. It got bigger over time. I saw a vet about it and her tendency to throw up (she's thrown up mucus for years, i believe due to anxiety.) Regarding both of those things, the vet said she was healthy. Now it looks bruised. I have prodded at it before so I'm not sure if I did something. She eats really well and has the same energy levels. I think it does hurt her when it's touched hard

1 Answer

Most Helpful Answer

Answered By Dr. Strydom, DVM

Veterinarian

Published on September 27th, 2023

Hello, thank you for using PetCoach.

Chances are that this is a sebaceous cyst. Sebaceous cysts are usually harmless, sack-like growths with a lining that is not cancerous. In dogs, most cysts develop from hair follicles. These cysts typically appear as single, clearly defined, firm or soft lumps located in the skin or just beneath it. They are often between 0.5 to 5 centimetres in size and may sometimes have a bluish colour. A cyst can release a thick, gray-to-yellow-brown cheesy substance if it bursts. Other terms for sebaceous cysts in dogs include infundibular or follicular cysts.

The lump needs to have a fine needle aspirate (FNA)/cytology to be sure of that diagnosis. Here is a link about the procedure and why it is done. It does not require anesthesia.

( https://vcahospitals.com/know-your-pet/cytology-fine-needle-aspiration-fna )

If it is a sebaceous cyst, it will be very obvious once the vet introduces the needle into the lump.

Hope this helps. Best wishes.

4Pet Parents found this answer helpful

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