The midfielder will undergo treatment, expected to last for three weeks, with the hope of a return to football by January.
Malt lymphoma is a relatively rare form of non-Hodgkin lymphoma and develops in lymphatic tissue such as the stomach, thyroid glands, lungs or the eyes. It is mostly caused by a bacteria called Helicobacter pylori and can be treated by a course of intensive antibiotics.
McPhail has made 10 appearances for Cardiff this season, but was sidelined at the start of the month in the 1-1 draw with Nottingham Forest with a thigh injury that required surgery.
Bluebirds legend Andy Legg is also cancer survivor. He said: “If he needs me, I’m here. He’s a fit lad; they’ve caught it in the early stages so that’s good news. I wish him all the luck in the world."
McPhail’s midfield teammate Gavin Rae also offered his support, saying: "He’s got everyone’s support here. It certainly puts football into perspective; all the players and staff at the club are rooting for him."
The club have requested that Stephen's privacy is respected during his treatment and recovery but supporters have been pouring in their get-well-soon messages on the club’s message board: www.cardiffcitystadium.co.uk/mb.