My rat has a soft lump under its skin with a brown spot. What is it?
Hi there, and thanks for using Petco Pet Education Center, formerly Petcoach! I'm sorry to hear about your lumpy rat friends. Small lumps (less than 1cm) in the skin that have a brown spot or head on them might be sebaceous cysts - a common condition in male rats where a gland in the skin gets clogged and swells with cheesy, white-yellow material. You mentioned that these lumps are soft and under the skin, however, which makes me think of another kind of lump. I don't see that you mentioned their ages, but if they are older rats (over 1.5-2 years old), I do start to worry about mammary tumors (yes, even in males!). These are extremely common in rats as they age, and may be benign or malignant, and may need to be removed, especially if they get large. I strongly suggest that these boys get evaluated by a vet to determine what these lumps are. There is a vet that sees rats near you - here is their info:
Acacia Animal Hospital
4205 N Campbell Ave, Tucson, AZ 85719
(520) 308-4225
In the meantime, if you'd like to repost with a picture, feel free to do so. I am also available for consultation if you'd like to discuss your concerns further. Good luck, and I hope that Lenny, Norm, Fred, and Herman stay happy and healthy!
Updated on September 23rd, 2025