As if chronic emphysema and a heart bypass weren’t enough to deal with, sources say TV legend Johnny Carson is now battling skin cancer!

The 77-year-old retired “Tonight Show” host has had lesions removed from both his head and arms, The ENQUIRER has learned exclusively. The growths were identified as basal cell carcinoma, a cancer that occurs most frequently on sun-damaged skin of the face, ears, neck, scalp, shoulders and back.

“Johnny has spent many hours outdoors sailing his boat or playing tennis on his courts up in Malibu,” said a source. “He rarely wore a hat or long-sleeved shirt, and for much of his life, he never wore sunblock. All of that sun damage caught up with him.”

Basal cell cancers can be successfully treated by removing the lesions or exposing them to radiation. But follow-up is crucial, experts say.

“Up to half of all patients will develop another cancer within five years,” Dr. Jerome Litt, assistant professor of dermatology at Case Western Reserve University, who has not treated Johnny, told The ENQUIRER.

Incredibly, Carson has undergone treatment for skin cancer before, a family friend revealed.

“Johnny’s had a number of lesions within the last several years,” the family friend said. “But as long as it’s not melanoma, he figures it’s not going to kill him.”

The ailing star has plenty of other health problems to worry about. He underwent quadruple bypass surgery following a heart attack in 1999, and has developed emphysema.

“Despite what he says in public, his emphysema has gotten worse,” the family friend said. “Sometimes he cannot exert himself without sitting down and resting every 15 minutes.”

When contacted by The ENQUIRER, Carson’s spokesperson and nephew, Jeff Sotzing, said: “I’m not going to comment on Johnny’s personal life.”