The 24-year-old left the Globe Arena to sign for League One Plymouth in the summer of 2017 after a successful three-year spell with the Shrimps.
Edwards has made 30 appearances and scored four goals for Argyle this season.
Morecambe manager Jim Bentley said: "The thoughts of myself, the board, the backroom staff, players and supporters are all with Ryan and his family.
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"He was a fantastic lad for us and always gave the club his all.
"I'm sure I am speaking for everyone when I say all our thoughts are with him.''
In a statement released on Thursday the club said: "Plymouth Argyle wish to advise that Ryan Edwards has been diagnosed with testicular cancer and is to undergo immediate surgery.
"The diagnosis was made when Ryan sought medical advice after experiencing symptoms which he thought prudent to have checked out.
"Ryan will obviously miss a period of football because of surgery but his physical health and mental well-being are our only priority.
"He has already proved to be the strong person we knew him to be by the manner in which he has reacted to this development."
Fans of all clubs are being asked to show their support for Edwards on social media using the hashtag #WithYouEddy