How long is it supposed to it take for skin cancer to kill someone if left untreated?

It Depends: There are several types of skin cancer & depending on the type, how bad it has progressed & the overall health of the person before the range is great. Skin cancers generally are very treatable and curable with the exception of some very bad forms so the question is why would someone not seek treatment for skin cancer? If non-treatable, the oncologist is the best person to give a timeframe.

Skin cancer : Some skin cancers evolve over years while some may grow and spread more rapidly over months such as the case with certain malignant melanoma. Skin cancer is highly curable when detected early.

Skin Cancer: The length of time one could survive with an untreated skin cancer depends on the type of skin cancer. The earlier the diagnosis and treatment the better the prognosis. There is no reason for an otherwise healthy person to leave skin cancer untreated.

Depends: The dangerous type of skin cancer is melanoma. If untreated, it can spread throughout the body into other organs like liver and lung. When that happens, it can kill someone within a year. But most skin cancers (squamous cell and basal cell) don't spread like that. They are usually cured by simply removing them. It is rare for skin cancer to lead to death.