Primal Sympathy by Lydia B

In order to find a cure for Scully’s cancer, Mulder fakes his own death without her knowledge. Once reunited, they embark on a journey of discovery that may end up costing them their lives.

This cancer-arc fic from 1997 had a fandom all of its own.  It's exquisite Scully-torture, but she's comforted with some hot horizontal mambo.  You can even choose to skip the smut if you're not into that kind of thing.... well I suppose it's remotely plausible that someone might not be here for the smut....