Can severe long term allergies cause Mast Cell Tumors?

My understanding is that Mast Cell Tumors affect cells that deal with allergies and inflammation. My dog is 6 years old and has had severe allergies since he was 1 year old. He takes allergy shots, apoquel, and ketoconazole currently. He had a weird growth pop up on his face that grew, shrunk, grew again, and now seems to be staying relatively the same size but sometimes looks more inflamed. He can't get into the vet until later this week, but after researching types of growths, I came across the information about MCT's and allergies, and I'm wondering if severe allergies make a dog more prone to MCT, or if MCT just causes an allergic reaction? I attached pictures, and it seems to change back and forth between all 3 looks on a daily basis.

Hello!  Mast cells do indeed play a part in allergy but I am unaware of a link connecting dogs that have allergies with a higher incidence of mast cell tumours.  I will double check my facts here and report back. The lump on your dogs' muzzle could be a mast cell tumour (MCTs famously 'can look like anything' and pop up when vets are least expecting them) but could also be a follicular cyst or histiocytoma or infected follicle, or any number of other benign or cancerous lumps.  Your research should have told you that even vets who specialise in skin cancer are not particularly good at predicting the biopsy results from a random lump by looking at it in situ on the dog. So:  What best to do?  Most vets will make the most educated guess they can  whether a lump is likely to be inflammatory or not.  They may elect to treat the hoped-for inflammation and monitor, or to take a sample of cells  - there are a number of ways to do this - to try to determine objectively what the main cell-type inside the lump is likely to be. I hope this helps.

Hello again!  I have looked through a some articles written for the veterinary press by expert vets regarding the diagnosis of mast cell tumours.   They are more common that I had thought (accounting for 21% of all skin tumours) and incidence has been linked to breed (famously boxers) but not, that I can find, to existing macroscopic signs of skin allergy.  However, as you mention, pulsating skin lumps would be typical and it's definitely a good idea to let your vet see this lump.

(Ps  'pulsating' was a poor choice of word there;  I meant expanding and contracting in size over time, not literally pulsating!)