Stage III uterine sarcoma is divided into stages IIIA and IIIB based on how far the cancer has spread within the pelvis (lower part of the abdomen between the hip bones). In stage IIIA, cancer has spread to the outermost layer of the uterus; and /or tissues just beyond the uterus; and/or the peritoneum. In stage IIIB, cancer has spread to lymph nodes in the pelvis and/or near the uterus.