Ovarian cancer is staged using the FIGO staging system and uses information obtained after surgery, which can include a total abdominal hysterectomy via midline laparotomy, removal of (usually) both ovaries and Fallopian tubes, (usually) the omentum, pelvic (peritoneal) washings, assessment of retroperitoneal lymph nodes (including the pelvic and para-aortic lymph nodes), appendectomy in suspected mucinous tumors, and pelvic/peritoneal biopsies for cytopathology. Around 30% of ovarian cancers that appear confined to the ovary have metastasized microscopically, which is why even stage-I cancers must be staged completely. 22% of cancers presumed to be stage I are observed to have lymphatic metastases. The AJCC stage is the same as the FIGO stage. The AJCC staging system describes the extent of the primary tumor (T), the absence or presence of metastasis to nearby lymph nodes (N), and the absence or presence of distant metastasis (M). The most common stage at diagnosis is stage IIIc, with over 70% of diagnoses.