WASHINGTON - First lady Laura Bush says she first thought a sore on her right shin that turned out to be skin cancer was an insect bite.

President Bush, right, accompanied by first lady Laura Bush, gestures as he addresses the media about his visit with troops wounded in Iraq and Afghanistan, Friday, Dec. 22, 2006 at Walter Reed Army Medical Center in Washington. [AP]

"Actually it never occurred to me to make it public," she told Bob Shieffer on CBS "Face the Nation" aired Sunday. "It was very minor. I thought it was an insect bite, actually, when I first got it, and then it just didn't get well."

The first lady said she had a biopsy done before the November election. The squamous cell carcinoma is a malignant tumor and the second most common form of skin cancer.

Mrs. Bush said she had it removed right after the election, adding: "I was never sick. I never felt badly."

She said she is glad the information about the tumor got out, and hopes it will prompt people to pay closer attention to possible signs of cancer. She blamed the cancer on the hot west Texas sun and her fair complexion.

"I never did a lot of sun bathing like some my friends did, because I didn't tan, really," she said. "But of course I played outside for my whole childhood (and) spent afternoons at the swimming pool and did those things that we all did growing up in Texas, and so I was out in the sun a lot."

White House officials were questioned about why the cancer was not disclosed publicly until more than a month after its removal. Mrs. Bush's secretary Susan Whitson said the procedure was a "private matter" but when asked by the media, "we answered the question."

The first lady was noted wearing a bandage on her right leg before the election. At the time Whitson said Mrs. Bush had a sore on her shin. In late October, Mrs. Bush had a biopsy because the sore was not healing, Whitson said, and it was determined to be a squamous cell carcinoma.

The cancer affects the middle portion of the epidermal skin layer. It is more aggressive than basal cell cancer, the most common form of skin cancer.