BOSTON -- Surgeons at Boston's Angell Animal Medical Center removed a 21-pound tumor from a Labrador retriever, the largest tumor veterinarians there had ever seen, WCVB-TV reported.

Warren, 13, fully recovered from the surgery to remove the tumor that had grown to one-sixth his body weight.

Warren was to be reunited with the surgeons at the hospital Wednesday afternoon.

"Warren had the largest external tumor that I have personally seen in my 35 years as a veterinary surgeon," said Dr. Michael Pavletic.

The tumor had grown so large it made walking difficult for the dog, and his breathing became increasingly labored.

"While the tumor required surgery, there were many life-threatening factors to consider as well, including Warren’s age," said Pavletic.

Surgeons faced the problem of dealing with the cavity that was created once the mass was removed.

"Although Warren’s tumor has the possibility of recurring, it appears to be a slow-growing tumor that we can monitor and help manage in the months ahead,” said Dr. Jean Duddy of Angell’s Internal Medicine Service

"Warren has since spent the past five months enjoying his lightened frame following the lifesaving surgery," Duddy said.