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My senior dog has a black, infected, growing lump. Is it normal?

Updated on September 23rd, 2025

Pet's info: Dog | Mixed Breed | Male | neutered | 75 lbs

My dog 13 year old dog has had a small growth since I've found him 3 years ago. It's grown a little since then, but now it looks like it might be infected. The growth is black and oddly over the course of those three years, it appears that another growth has grown over that. I've had it tested several times, each coming back negative for cancer. But I'm wondering what it could be and if something like this is normal? The growth isn't very attached to the actual leg, it's mostly just long.

1 Answer

Most Helpful Answer

Answered By Summer Walker, DVM, MS

Veterinarian

Published on August 3rd, 2017

Thank you for using Petco Pet Education Center, formerly Petcoach! A mass on the skin is never "normal," but it is not uncommon to see skin masses appear as patient's age. It is virtually impossible to be able to distinguish a benign versus a malignant (cancerous) growth based on appearance alone, which is why we typically rely on biopsies or fine needle aspirates for diagnosis. Fine needle aspirates are less invasive and do not require sedation/anesthesia, but only give us a small picture of the mass since we are only able to sample the cells present within the needle used. Removal of a mass with submission for histopathology (biopsy) is always preferred and recommended for masses that change in size or shape. If the mass on Bradley's leg is changing, continually infected, or is irritating/painful for him, it would be best to have the mass removed and submitted for histopathology. Even if the mass is benign, it is serving as a source of irritation/infection for him, and could potentially become malignant in the future.

1Pet Parents found this answer helpful

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