Please help! what happens in cancer cell biology?

Man, there are : ..Entire books meant to answer that. Cells have instructions in their dna that establish their behavior. Sometimes those instructions are changed (mutations) and the cells start dividing too much, "learn" how to spread, and bypass their "self destruct" mechanisms. That ultimately leads to a malignancy. It is way more complicated that that but i ain't got space. Try the acs or the nci websites.