system
Given the following post, respond as if you're commenting on Reddit:
human
Eli5 Why can’t cancers just be removed?

When certain cancers present themselves like tumors, what prevents surgeons from removing all affected tissue and being done with it? Say you have a lump in breast tissue causing problems. Does removing it completely render cancerous cells from forming after it’s removal? At what point does metastasis set in making it impossible to do anything?
gpt
Some cancers can be, but the surgeon has to balance getting all of the cancer and none of it breaking off and not damaging the rest of the organ where the cancer is which may be keeping the person alive.