Is this an eye tumour?

Hello! 7 year old black Labrador, no ongoing health issues. 32kg fit, healthy, raw fed diet. Before starting, we have already taken him to the vet today when we noticed it had grown and are waiting for a vet that specialises in ophthalmology to review his pictures and get back to us in the week. so I noticed about a month ago a small black dot on the bottom of my dogs iris. I mentioned it to my partner who had a Quick Look, couldn’t see it and said it must’ve been his inner eyelid stuck or something and not to worry. fast forward today, I was sat in front of a window so the light shone on his eye enough for me to see that this black dot was in fact there and had gotten bigger. after a quick google search I found that there is such thing as eye tumours and Labrador retrievers have a pre disposition to them. I am looking for advice as I have honestly never heard of this before. We are hoping it is nothing serious but in the event that this is worse case scenario, what does our near future look like? pictures for reference: December: march: : today:   Thanks in advance  

Hello and thank you for this excellent question.   Perhaps there are experts who can tell you with certainty what that is from those pictures, but it is beyond my skills; I'd want to look at that from several different angles (ie with an opthalmoscope) to guage the depth and might even ask for a sample or more advanced tests / referral before forming an opinion.  I assume that the lesion is in the anterior chamber - ie in front of the iris but behind the clear, thin cornea at the front - which suggests to me that it could be a tumour, but at the same time could also a uveal cyst, foreign body, parasite or haemorrhage (a bleed within the eye) as well as a problem of the superficial eye or cornea.  A full body and ocular examination (even with sampling) might be needed in order to diagnose it fully.  As with any change to the eye, please report it or any changes to the vet or emergency vet when you see them; they can prove urgent.  Never diagnose based on what you think is 'common' within a breed or species; although common things are common, exceptions also occur.   Your vet should begin a logical process towards finding out, in a timeframe appropriate to the case.   Best of luck.