[hwillis]

The most obvious way is that carcinogens affect parts of the body differently. Iodine collects in the thyroid, some compounds accumulate in the gut, alpha and beta affects the outer layers of the body.

Epigenetics can cause different parts of DNA to be more or less exposed in different parts of the body. There are also indirect effects from chemicals- some carcinogens can cause changes in proteins, or be bound to proteins, which can cause them to be around certain regions of DNA more.

Mostly though you see that kind of thing more in viral/bacterial cancers- a sizeable percentage of all tumors are caused this way.