Dear Doctor: A cancer so rare most doctors have never seen it — and it starts in a finger's sweat glands

Dear Doctor Roach: Do you know anything about aggressive digital papillary adenocarcinoma? My 39-year-old nephew was just diagnosed, and his parents are searching for answers. He’s getting scans to determine whether they should amputate his finger. As far as we know, it hasn’t metastasized. — A.M.