Man would be more accurately named C.J. Spender. A close, personal friend of Fox Mulder
's father, and co-conspirator in dealings with extra-terrestrials.
He is not named because he may
have cancer due to his ever-present Morley cigarette
s, but rather, was implicated somehow when Agent Scully
discovered she had an inexplicable implant
beneath the skin at the nape
of her neck.
As soon as the implant was removed, she developed cancer, but when it was replaced, at Spender's suggestion, her illness
...hence "the Cancer Man".