She doesn't have this anywhere else? The wound being on the shoulder, it could be mites (Cheyletiella). Or it could just be a normal abrasion. Animals always find ways to hurt themselves when we are not looking.
I would look at her completely (especially around the tail) to make sure there is nothing else. If you don't find anything, you can disinfect with a bit of betadine or biseptine (don't know if they are under the same name were you are) and look at it everyday. If it disappear, it's just a normal wound. If it doesn't or, worse, if it spread, it's probably a parasite and you'll need a treatment for it.
Skin cancer is not all that frequent in rabbits. It's often a spread of another cancer (often, uterine cancer in intact rabbits as it's the most common - considering her age, your rabbit is very much at risk if she wasn't spayed, the risk is around 80%) and from what I've seen it's generally more of a lump (something like an abscess). I've not seen cancers looking like your photo, but I might be wrong on that.
