What's this draining lump on my senior cat's cheek? Is it serious?

That is very oddly discolored gunk for sure. I would certainly clip (if you're able) around the area to see if it looks infected or can be kept clean at home (clean washcloth, Elizabethan collar to prevent pawing at or licking it, keeping the area trimmed and dry). If Gremlin won't let you look at it or clean it properly, more discharge is coming from it, or it's very large/rapidly changing in size, a vet visit is a good idea. They can safely clip back any hair to make sure there aren't other pockets of infection, can clean the area, and may suggest taking samples if they suspect something more than a clogged pore or minor abscess.

Hi. It appears to be a mass that is oozing near that nipple area. This could be an infection or an actual mass. We get concerned with older female pets who have masses on the mammary glands. They can get benign masses, but they can get cancer as well. I'd get her right away to have it checked and sampled asap

This may be an abscess, a cyst or a tumor. You should have it examined by your veterinarian, as it is not possible to distinguish these by just looking at a photo. An abscess can usually be treated with antibiotics and/or be lanced, and a cyst can be evacuated. To identify a tumor, your vet may want to do a fine needle aspirate (he takes some material from the bump with a needle and then looks at it under the microscope) to determine whether the mass is concerning.

It is possible that it is a tumor, and could possibly be infected. I would encourage you to have him evaluated by your veterinarian soon. They may recommend antibiotics and possibly removal. Best of luck and thank you for using Pet Coach.

This might need to be removed surgically, the best way to find out is to take her to the vet, they will aspirate a small sample with a syringe and needle from the lump, then they will send it to the lab to find out if the tumor is cancerous or benign. if it is cancerous it will need to be removed for sure, but even if it is benign, due to the symptom it causes, your vet might advise surgical removal.

Pets can get many types of lumps and bumps. Most of these tumors will be benign but some will be malignant and you can't tell by looks. Here is a helpful link discussing the various types of skin masses in general: https://www.petcoach.co/article/lumps-and-bumps-on-your-pet/ Since you are noticing the mass changing, I do recommend to have it checked out to be safe. The doctor may recommend to aspirate the mass to examine the cells under a microscope. That is one of the best ways to know what it is and if further action is needed. Hopefully it's nothing serious.

Poor guy. This appears to be a mass that has ulcerated and is now bleeding. When masses rupture like this they are a constant source of infection and discomfort for the pet. I recommend scheduling an appt with your vet to discuss having this mass removed surgically at this point. In the meantime you can try cleaning it with Betadine diluted 50:50 with warm water to antiseptically clean the area and prevent infection. You can also place an e-collar on Harley to deter him from chewing or licking at it , which will only make it more irritated. Best of luck with Harley and getting this mass removed. Take care.