
Hi Sarah,
I found a lump on my 3-year old Cairn's front leg two weeks ago. Took her to the vet and he said it looked like a tumour and not a cyst. He said he cannot tell what it is without removing it and biopsy, but it is in such a bad place (right behind her knee) that it needs to be removed when it's still small even if it's benign so there is enough skin to close the wound properly.
So Wednesday at 8 am I dropped Abby at the vet for surgery. At 11 the vet called to say he was not going to remove it because it had shrunk so much from the week before when he saw it. (I thought it was smaller, but chalked it up to my imagination.) Anyway, he's given me some cream to rub on it twice a day and it is getting smaller and softer.
However, the vet said that because he does not know what it is the whole thing could reverse in six weeks. So I too am worried about Abby's lump. The vet mentioned mass cell tumours which if caught early are highly curable just by surgical removal. If like me you always imaging the "worst" - mass cell is the most common type of cancerous tumors in dogs.
Meanwhile - my other 3-year old Cairn has a lump on his back which the vet said was in impacted hair follicle. That was in December and it's still there - so it seems I cannot get away from dogs and their lumps. :-(
Your vet cannot absolutely tell the difference between a cyst and a tumour without surgery or needle aspiration at the least. That's according to my vet - who is not given to modesty, if you know what I mean. So your puppy could very well have a cyst - they either get smaller, stay the same, or grow larger - so the fact that the lump has grown does not mean all that much really.
I will be thinking of Tink - try not to worry too much.