Red Bumps Turned Ulcerated Sore/Tumor

Hey all, been striking out with answers at our vet and hoping to find some additional opinions/direction here. We have a 12 year old dog in generally good health, she's had arthritis for some years which is managed and 6-8 months ago started having minor skin flakes/patchy fur in a couple spots that initially improved with fish oil & probioitics, then recurred recently so lab work was done which showed a lower end of normal thyroid activity. About 2 weeks ago we started her on meds for that. At the same visit for her thyroid bloodwork, a ~1/2" red bump that had been developing under the skin on her back was opened up into a sore while examining it. Vet said it was a hotspot (another tech we know saw it and agreed), we got an antibacterial/steroid spray and went on our way. It seemed to be healing, scabbing over slowly until the scab fell off. Then it started growing fairly rapidly, and ulcerated. We went back to the vet to get a biopsy done, which took a week to get results while it kept growing, and our vet concluded it was likely an infected insect bite or similar, and started antibiotics on Aug 22. Full lab report language below. August 23 I noticed another small bump on her back which was scabbed over (this one maybe 1/4" scab on a 1/2" bump, about half of the first one when it scabbed). Decided to give it a day or 2 to see if it responded to antibiotics. Yesterday (Aug 26) we noticed a third small bump on the side of her back, this one not scabbed. It's just reddish and raised. Now 6 days into antibiotics, the first large ulcerated "sore/tumor" looked grayed out and has dried blood on it but is not actively ulcerated, but does seem to still be spreading outward and has squared raised edges. Planning to go back to the vet this week, but growing more concerned by the hour here. Help?!? Pic 1: August 19 Pic 2: August 22, first day of Cephalexin Pic 3: August 27, day 5 of cephalexin INTERPRETATION: Haired skin (dorsal midline): Consistent with dermatitis, ulcerative and pustular, lymphocytic and histiocytic, marked, with scattered eosinophils. See comments COMMENTS: The submitted tissue includes ulcerated skin with a marked cellular infiltrate throughout the dermis. The infiltrate is somewhat mixed and largely reflects what appear to be macrophages and lymphocytes predominantly. There is some degree of crush artifact with nuclear streaming that somewhat obscures the cellular detail. There are also few scattered individual eosinophils. The pattern of infiltrate could be suggestive of a regressing histiocytoma, or may represent an inflammatory reaction due to previous local trauma or insect bite. There is no overt evidence of a malignant neoplastic population. Based on the histologic appearance, excision of the affected region would be likely to prove curative. Again, please note that there is some loss of cellular detail and as these are relatively superficial biopsies, there may be additional deeper changes not captured within these incisional biopsies. Results should be interpreted in conjunction with additional clinical information. HISTOPATHOLOGIC DESCRIPTION: Haired skin (dorsal midline): These sections show fairly extensive ulceration and loss of the epidermis. In one of the sections there is a large intracorneal pustule with sheets of degenerate neutrophils admixed with areas of hemorrhage and proteinaceous fluid. Most of the tissue consists of dermis with a marked cellular infiltrate. There is some degree of crush artifact with nuclear streaming and loss of cellular detail, however, most of the cells appear to be a mix of lymphocytes and macrophages. There are small number of individual eosinophils scattered throughout.

Hello - and that does look sore.  Hypothyroidism is an auto-immune condition - one of those diseases in which the immune system seems to get simultaneously overexcited and less effective.  There are many forms of autoimmune disease, also including things like rheumatoid arthritis, various skin diseases and diabetes.  It is not uncommon for a pet with one autoimmune condition to develop another. Reading the report, it sounds as though this lesion was a essentially lump of inflammatory (immune system) cells, which might have been started off by something as innocuous as an insect bite, but over-reacted / got over excited and grew out of control? Could it be related? It is great to hear about your vet working the case up.  They have had the lesion tested and found it to be inflammatory, although it must be quite frustrating that the answer to treating the lesion so far appears to have been to cut the damaged skin away.  I wonder if there is treatment that can be engaged that might prevent a sore's development as soon as you notice it coming on.  This is beyond my knowledge but I wonder whether your vets have an opinion?  Or whether speaking to the pathologist who did the work might yield any more information?  (in my experience, pathologists like finding things out and are very engaged people to talk to about a case). I also wonder whether there are more investigation s that your vet would like to do, or whether they feel that they have taken the work-up as far as they can, and that a referral may be the next step?

Thank you for the quick reply! Glad to hear this seems like a good course of action being taken. Our vet is out of the area this week so hopefully next week we can get in and see possible next steps. In the meantime will see if we can get a hold of pathologist for any potential answers.

Great to see your response.  Your vet may have a pathologist that they deal with - they might contact the one who wrote the first report that you included for example, if they need to know any more.                      

Great to see your response.  Your vet may have a pathologist that they deal with - they might contact the one who wrote the first report that you included for example, if they need to know any more.