What Do Pathologists Study and Why Is This Helpful in Cancer

What do pathologists study and why is this helpful in cancer treatment?

A) They study the hereditary path the cancer has taken through a particular family so living family members can be warned they might be at risk.
B) They study disease, so they try to figure out what's gone wrong with the cells in a particular case of cancer, allowing for more precise treatments.
C) They study the sympathy of the doctors treating cancer, ensuring that they are considering how worried the patients might be about the diagnosis and treatment.
D) They study the path the cancer has taken in moving through the body which allows for more accurate targeting of treatments.
E) They study people who have been treated for cancer to ensure the cancer is really gone.