>>13990954>Why does the treatment not simply take away a solid square foot of skin surrounding the cancer?Well that is sort of what they do, obviously over less space since you want the patient to survive. There's lab testing to figure out if it's been completely or only partially removed. For a serious skin cancer like melanoma that's basically what has to be done. No guarantees, it's the most deadly kind of skin cancer.
Luckily melanoma's quite rare! Basal cell is the most common type of skin cancer, there's a good chance you might get it at some point, even if you're not light skinned. Very slow growing, you could almost say non-lethal, people sometimes spend years avoiding treatment just to have a very obvious red growth sticking out of their skin. Getting a minor deformity like a scar in the aftermath of moh's surgery. Squamous cell is the second most common, similar to basal cell but statistically a bit more dangerous and fast growing.
There's surgical excision. For non-melanomas there's also curettage & cautery, spraying liquid nitrogen, etc lots of different approaches.
https://www.youtube.com/watch?v=Ac64LrXIzm8 
