Mast Cell Tumor or Something Else?

[Blueskye]

I have a 12.5 year old orange tabby. He's always been healthy despite being quite a big boy most of his life, and currently sits around 20 pounds.

For about a year now he's had a lump on the top of his head. When I took him to the vet in August she stated she believed it was just a cyst, but the more time goes on, I dont think that's the case. As you can see, the lump has some black spots and red sort of crust in certain areas.

At his last exam in August all of his lab work was normal and as of this posting he doesn't have any behavioral changes, thankfully. I made an appointment for him to have a dental cleaning in April and at that time they're going to hopefully remove the mass as well. I'm wondering if that's too long to wait? Does this look like it could be something else, or is it likely cancer? He allows me to freely touch it, so I'm assuming there's no pain/discomfort and he doesn't ever lick or scratch at it.

 

[Maurey]

It doesn't *quite* look like what I've seen mast tumour cells present like, personally, however it's hard to know 100% for certain without getting an analysis done, as they can sometimes present very differently. Viewing a fine needle aspiration under the microscope would give a concrete answer -- around 90% of cutaneous lumps on adult cats are benign.
If it's within your finances, and your cat isn't unduly stressed by vet visits, I'd suggest requesting a fine needle aspiration for the lump, just to confirm what it is. It's relatively non-invasive, and doesn't require anaesthesia, ime.
From my experience with such things, it's not exceedingly likely to be a mast cell tumour, as his bloodwork is normal, he's not had any noticeable behavioral changes, and he's not developed any more masses. That said, definitely best safe than sorry -- this isn't the type of thing realistic to definitively diagnose from a photo, imo.

 

[fionasmom]

It does not look like melanoma or hemangiosarcoma to me; my GSD had melanoma. The crusting bothers me, but that does not mean this is cancer. If an FNA can be done it would give you an answer and then removal could be done later if necessary. If it were to be cancer, I think that it could be removed with clean margins....but remember that most lumps are not cancer so don't go down that road yet.