Researchers at the Mayo Clinic examined 915 patients with endometrial cancer who had surgical treatment at the clinic from 1984 to 1996 -- and who had no other malignancies diagnosed within five years before or after the initial diagnosis.

They identified as risk factors specific characteristics of tissues that had been removed during surgery and analyzed under a microscope. They said other risk factors included whether the tumors were confined to the uterus or if the disease had spread outside the uterus.

The study's findings are important for women deemed at risk because they might need additional treatment, which physicians should consider in their plans for their patients, said Karl Podratz, the study's lead researcher.

In the United States, endometrial cancer is the most common disease of the female reproductive tract. Only breast, colon and lung cancers are more prevalent in women.

Researchers estimate that during 2004, about 40,320 new cases of endometrial cancer would develop in the United States and 7,090 women would die from the disease.