Cancer can go anywhere, but "usually" has a known path of travel like metastasizing through the lymph nodes, blood, vein or nerve lines, other nearby structures, and there can be secondary, synchronous or metachronous cancer from field cancerization from exposure to carcinogens, which is not always just tobacco. Clear margins may also differ between doctors what is a clear margin or not, I forget the size areas, but like one may consider 5mm clear, another may say 1cm, and then want further treatment to get any microcosmic cancer.

Good luck.