Bella had a histiocytoma on her neck from November to January. We were told that it would most likely fall off within 3 months, and she had it for about 6 weeks without any surgical intervention. We sometimes cleaned it off with hydrogen peroxide, but for the most part, we left it alone. It bled a lot, and we had to cover our furniture with sheets (although we probably could have put a t-shirt on her.) Here's how her tumor progressed:
The day I took her to the vet for it, about 1 1/2 weeks after I first noticed it - it was pretty irritated and bloody (early December):
Pretty nasty still
Scabbed and healing
Almost completely healed - with pink new skin (early January)
Her hair has almost totally grown back in that area, and you can barely tell she had a big nasty tumor there.