Why Are "False Positives" in Diagnostic Tests for Cancer Rather

Why are "false positives" in diagnostic tests for cancer rather common?

A) Most diagnostic tests for cancer are relatively new and have not been well tested.
B) Cancerous cells are nearly identical to normal cells, so often a doctor will see what looks like a cancer cell but it isn't one.
C) Diagnostic tests are generally quite broad to ensure that the doctor doesn't miss a cancer that's there.
D) Patients are sometimes unhappy to have paid to get tested "for nothing" so a doctor follows up as if the test is positive when it isn't justified.
E) Hardly anyone actually gets cancer, so usually when something looks like cancer, that's what it turns out not to be.