It's down to the susceptibility of different cells to mutate. This will be highest in soft tissue, high concentration places of carcinogens and how these enter the body and then take up residence, the rate at which the mutated cells have the ability to reproduce, the access to pathways within the body that allows the cancer cells to spread (lymph system etc.) and areas of the body less protected from UV etc.
So oral and nasal passages, lungs, the stomach, intestines, vital organs. skin etc. will succumb to cancer more readily than extremities because the mutation catalysts have the highest probability of collecting in these places.