According to The Mirror, the 32-year-old could lose his voice if he doesn’t have the lump removed immediately.
Ryan, who has fronted boy band Blue for over a decade, is said to be ‘devastated’ by the diagnosis - especially as he was meant to be touring later this year.
Lee saw a specialist in London on Friday who found a ‘huge white limp on his vocal chords’ The Mirror reported.
‘He had known something was wrong for a long time and even feared it was cancer,’ a source told the paper.
But despite getting the all clear from the big C, Ryan was still understandably devastated to hear that he’ll require emergency surgery to remove the cyst.
It is thought that if the star has surgery to remove the lump, which is growing quickly, he will be unable to speak, let alone sing, for some weeks after.
2015 has already been a difficult year for Lee, who declared himself bankrupt in April.