Tough guy actor MICKEY ROURKE recently underwent a battery of cancer tests at two New York clinics!

The 60-year-old former boxer had been complaining to doctors that he was feeling sluggish and losing clumps of hair – and he was certain he was suffering from potentially deadly thyroid cancer, say sources.

But it seems to be just a scare. While Mickey’s life does not appear to be in immediate danger, doctors discovered that he has an enlarged thyroid, and they’ve ordered additional testing to determine the cause.

One medical expert tells The ENQUIRER that a larger-than-normal thyroid – the butterfly-shaped gland located at the base of the neck – could be caused by cancer.

“Mickey was scared to death,” a source divulged. “He was absolutely convinced he had cancer when he went in for testing.

“His brother Je died of lung cancer cancer seven years ago, and ever since, Mickey’s believed that the same fate would befall him.

“He also had a friend who suffered from a brain tumor, and he did not want to go through the same thing.”

About six months ago, says the source, Mickey went to his regular doctor because he wasn’t feeling well. After numerous tests, it was determined that his thyroid was “significantly larger than it should be,” according to the source.

“They wanted Mickey to undergo more tests and, need­less to say, he was nervous and worried,” said the source.

Noted California-based thyroid expert Dr. Richard Shames, author of “Thyroid Mind Power,” says there are many things that can cause a person’s thyroid to become enlarged, including cancer.

“Although it’s a cancer that doesn’t usually spread, it can kill and should be checked out,” Dr. Shames explained. “Doctors will do an ultrasound  the shape and condition of the gland.

“If it seems that a nodule or growth is causing the enlarge­ment, they’d do a biopsy to determine whether the growth is benign or malignant.

“If it’s malignant, then surgeons would perform a thyroidectomy to remove the gland and check surrounding lymph nodes for any evidence that the cancer has spread.”

Dr. Shames added that even benign growths should be care­fully monitored, because they can become cancerous.

ACCORDING to the American Cancer Society, there were more than 56,000 new cases of thyroid cancer in the U.S. in 2012, and an estimated 2,700 people died from the disease.

Mickey, who was nominated for an Oscar for his role in “The Wrestler,” has had his share of medical problems over the years.

He was three fights away from a cruiser­weight title when he was forced to retire for neurological reasons. He’s also undergone a series of surgeries on his face to rebuild his bashed-up nose with carti­lage from his ear. But the recent cancer scare has apparently turned his world upside-down.

“Mickey’s going back for more tests,” added the source. “He’s still on pins and needles.”