The 67-year-old performer announced on his Web site this week that he has been diagnosed with Adenoid Cystic Carcinoma, which is affecting the lower region of his tongue.
"It's a bad news, good news situation," Tork said on his Web site. "It's so rare a combination (on the tongue) that there isn't a lot of experience among the medical community about this particular combination. On the other hand, the type of cancer it is, never mind the location, is somewhat well known, and the prognosis, I'm told, is good."
Tork said he hopes to perform a planned gig with his new blues-rock band, the Shoe Suede Blues, in Manchester, Conn., this June.
The BBC quoted Tork's publicist as saying the extensive surgery the musician underwent Wednesday went well and that Tork is expected to begin radiation treatment after he recovers from the operation.
"I am extraordinarily grateful, amazed and humbled by the encouragement, affection and support I've received so far," Tork said of the reaction from friends and family to the news of his illness.
The Monkees had numerous hits in the 1960s, including "I'm a Believer," "Daydream Believer" and "Pleasant Valley Sunday." The group, which consisted of Tork, Davy Jones, Micky Dolenz and Michael Nesmith, also starred in a television sit-com.