I had one of these when I lived in Phoenix (they don't do very well in Minnesota, so I left it there :). It grew pretty slowly, but I didn't have it as long as you describe. They are probably rare as far as being naturally occurring goes, but I saw them regularly in stores and sales. I have some recollection that the monstrose ones didn't bloom very much, either.

Any chance of pictures? What size? Can you remove them from the leaf easily?

Seen this before, but have no idea what it is or what causes it. I found it to be a cosmetic blemish and nothing more. Harry

The cancers on my forehead and nose were squamous cell, and the one near my eye was basal cell. For several years, I had what appeared to be a slim oval-shaped freckle on my forehead. Totally flat and smooth. Then I noticed that it had gained some "depth" to it, and was slightly "textured." Not rough, exactly, but no longer completely smooth. It didn't itch or hurt. But, I've always had long nails, and I began to notice that if I scratched my forehead for any reason, a fingernail would seem to "catch" on that spot so I went to the dermatologist to have it removed. In looking at it, the doctor didn't think it was anything to be concerned about, but I said I wanted it gone, so he removed it. In California (I don't know about other states/countries), if something is removed from someone's body it must be sent to pathology for analysis. The report came back that it was squamous cell carcinoma. So, I had to go back to have surrounding tissue removed to ensure that all of the cancer cells had been removed. The cancer on the side of my nose started out as a bump. Didn't look at all like a pimple. Didn't hurt or itch. No odd color to it -- it matched the rest of my skin. But it was "in my line of sight." That is, I always noticed it there unless I had my eyes closed. It bugged me. I was in a lot of meetings (for my job) with a lot of high-level folks, and I became really self-conscious about it. So, I went to the dermatologist to have it removed. Again, the pathology report showed it was a squamous cell carcinoma. Related side story -- I first started wearing glasses when I was in the 5th grade. I am extremely nearsighted. Seems my prescription would get stronger and stronger every year. My nose has a very small (narrow) bridge, and the weight of my glasses (even with very lightweight frames and lenses) caused the skin on both sides of my nose to become very raw. My medical doctor told me that I should switch to contacts, saying that if I didn't, I would end up with skin cancer on my nose. I didn't want contacts. I had several close friends who wore contacts and they were always having one problem or another with them. So, I continued to wear glasses for several more years. Finally, I couldn't take it any longer and switched to contacts. And I ended up with skin cancer on my nose. The cancer near my right eye was, again, a bump, but smaller than the one I'd had on my nose. Again, it was in my line of sight and bugged me. It was about halfway between the inner corner of my eye and the tear duct. Because of the proximity to the tear duct, my dermatologist sent me to a specialist in Moh's surgery. The pathology report on that one was basal cell carcinoma. I've looked at lots and lots of photos of skin cancers, but I've never seen one that looked anything at all like any of the three I had. Therefore, my advice to folks would be that if you have an existing spot or mole and it suddenly changes, get to a dermatologist to have it removed and analyzed. If you suddenly have a growth where you didn't have one before, get to a dermatologist to have it removed and analyzed.