The tumor is found in one or both ovaries. Stage I is divided into stages IA, IB, and IC. In stage IA, the tumor is found inside a single ovary. In stage IB, the tumor is found inside both ovaries. In stage IC, the tumor is found inside one or both ovaries and one of the following is true: (1) tumor cells are found on the outside surface of one or both ovaries; or (2) the capsule (outer covering) of the ovary has ruptured (broken open); or (3) tumor cells are found in the fluid of the peritoneal cavity (the body cavity that contains most of the organs in the abdomen) or in washings of the peritoneum (tissue lining the peritoneal cavity).