Former Virginia Gov. John N. Dalton, who has been mentioned as a possible Republican candidate for governor in 1985, has an early form of lung cancer, doctors at the Medical College of Virginia said today.

Dalton, 52, underwent surgery at the hospital Monday and doctors removed the lower lobe of his right lung.

A pathologist's report released today confirmed the diagnosis of adenocarcinoma, one of the subtypes of lung cancer.

Dr. Lazar Greenfield, Dalton's doctor and chairman of surgery at the college, said in a statement that while a tumor was found in a lymph node "We are optimistic. . . all of the malignant tissue" was removed during Dalton's four-hour operation.

Dalton, who served as governor from 1978 to 1981, was admitted to the hospital Aug. 11 after a routine medical checkup showed a spot on his right lung.

Dr. Greenfield said Dalton, a nonsmoker, was in good condition.

"He has been able to visit with family members and is in good spirits. He is up and around," the physician said in a statement.

It usually takes about two weeks to recover from such surgery, the doctors said.

Carole Roper, a hospital spokeswoman, said there is no information yet about what further treatment Dalton may undergo.

A millionaire lawyer, businessman and farmer from the town of Radford in southwest Virginia, Dalton joined the Richmond law firm of McGuire, Woods and Battle when his term ended in January 1982.

He had served as the state's lieutenant governor from 1974 to 1978 and has been mentioned by party officials as a possible candidate for a second term as governor, although he had not formed any fund-raising committees or taken other steps.