It's the second time the tumour has appeared. The first one, which was benign, was removed a few years ago.
"When I had the first tumour my little girl was only three-months-old. She is now five and is growing up. It has made me realise what is important in life," Legg told the Wales on Sunday.
"I just hope having the entire gland removed will be an end to everything. I am ready to go into hospital. I kept the first benign tumour private. It came overnight and happened when I played with Cardiff City. At that time, the club was struggling and we were relegated.
"I just kept it away from fans for my own personal reasons."
Legg has been told there is a 50/50 chance this one could be cancerous. Leggy is still playing for Peterborough and made his 700th league appearance last weekend. He does not expect his latest op to get in the way of his football.
Good luck to Andy and fingers crossed all will be OK.