RALEIGH, N.C. — When a woman tested for breast cancer hears the word benign, it is a huge relief, but a study in the

New England Journal of Medicine

said there is still cause for concern. Some benign results may pose a risk of eventually leading to cancer.

In 1998, doctors found a lesion in Sister Kathleen Murphy's breast. It was benign, but a year later, another lesion appeared. This time, it was cancerous.

"It was malignant. I was absolutely shocked. I wasn't expecting it," she said.

Breast surgeon Dr. Dana Monaco said some patients with a benign lesion have an increased risk of breast cancer later on. It all depends on the type of lesion.

"The risk is higher, depending on what the benign disease is," said Dr. Dana Monaco, of Mercy Medical Center.

There are basically three types of benign lesions. A study in the

New England Journal of Medicine

said each one poses a different risk.

The most common is called non-proliferative. It poses the lowest risk -- almost no increased risk at all, unless there's a family history of cancer. The risk factor doubles with a proliferative lesion -- the kind Murphy had. The highest risk comes from atypical hyperplasias. They are considered precancerous.

Vicki Wilkinson recently found out she has an atypical hyperplasia. She was relieved that is not malignant, but she knows it requires close follow-up.

"I've been back twice since August for check-ups and mammograms," she said.

Officials said frequent checks are the best way to find and treat the disease early.