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