Lambo, 28, is fully cleared for all baseball activity just three months after undergoing surgery for testicular cancer, having avoided radiation treatment. He's been working out on his own for nearly a month and hopes to latch on with a winter ball team.
"I think he's in a good place," A's manager Bob Melvin said. "I talked to him some earlier about this maybe affecting him for a while now. Now he knows, he's got it cleared up and seems to be in really good spirits, so it's really good to have him here."
Lambo was on the A's Opening Day roster but had just one at-bat before being optioned to Triple-A Nashville, where he hit .255 with four home runs in 56 games ahead of his diagnosis. Lambo was immediately treated at Vanderbilt University Urology Clinic.
He said Monday he has a swollen lymph node that is being monitored, "but I'm not going to just sit around," Lambo proclaimed. "I want to get back out there and play a full season."
The A's put Lambo on the big league roster and have since kept him there by way of the 60-day disabled list, allowing the outfielder to receive half a season's worth of big league salary -- a gesture he said he greatly appreciates.
"Everyone here has been so great to me," he said. "That's a big reason why I want to get back out there with them."
Jane Lee has covered the A's for MLB.com since 2010. Follow her on Twitter @JaneMLB. This story was not subject to the approval of Major League Baseball or its clubs.