Ovarian cancer (staging)

The most commonly adopted ovarian cancer staging system is the FIGO staging system. The most recent staging system is from 2014 :

CT is considered the best imaging modality for staging ovarian cancer. .

stage I: tumor limited to the ovaries
- stage Ia:
  - tumor limited to one ovary
  - capsule intact
  - no tumor on ovarian surface
  - no malignant cells in ascites or peritoneal washings
- stage Ib:
  - tumor involves both ovaries; otherwise similar to stage Ia
    - capsule intact
    - no tumor on ovarian surface
    - no malignant cells in ascites or peritoneal washings
- stage Ic:
  - tumor involves one or both ovaries, with any of the following:
    - stage Ic1: surgical/intraoperative spill
    - stage Ic2: capsule ruptured before surgery, or tumor on ovarian or fallopian tube surface
    - stage Ic3: malignant cells in the ascites or peritoneal washings

stage II: tumor involves one or both ovaries with pelvic extension or primary peritoneal cancer (below pelvic brim)
- stage IIa: extension or implants on the uterus or fallopian tubes
- stage IIb: extension to other pelvic intraperitoneal tissues

stage III: tumor involves one or both ovaries or fallopian tubes with cytologically or histologically confirmed spread to the peritoneum outside the pelvis and/or metastasis to the retroperitoneal lymph nodes
- stage IIIa: positive retroperitoneal lymph nodes and /or microscopic metastasis beyond the pelvis:
  - stage IIIa1: positive (cytologically or histologically proven) retroperitoneal lymph nodes only
    - stage IIIa1(i): metastatic retroperitoneal node measuring ≤10 mm
    - stage IIIa1(ii): metastatic retroperitoneal node measuring >10 mm
  - stage IIIa2: microscopic extrapelvic (above the pelvic brim) peritoneal involvement with or without positive retroperitoneal lymph nodes
- stage IIIb: macroscopic peritoneal metastasis beyond the pelvis up ≤2 cm in greatest dimension, with or without metastasis to the retroperitoneal lymph nodes
  - includes extension of tumor to the capsule of liver and spleen
- stage IIIc: macroscopic extrapelvic peritoneal metastases >2 cm in greatest dimension, with or without metastasis to the retroperitoneal lymph nodes
  - includes extension of tumor to the capsule of liver and spleen

stage IV: consists of distant metastasis, excluding peritoneal metastases, and includes the following:
- stage IVa: pleural effusion with positive cytology
- stage IVb: distant metastases
  - parenchymal metastases and metastases to extra-abdominal organs (including inguinal lymph nodes and lymph nodes outside of the abdominal cavity)

bilateral ovarian tumors may represent stage I disease, but represent metastases in ~30% of patients
one of the potential difficulties in differentiating stage II from stage III disease is differentiating between involvement of pelvic and extrapelvic peritoneum
the majority of ovarian cancers present as stage III
presence of metastatic lymph nodes is important, but the number of nodes does not carry prognostic significance
the amount of peritoneal involvement carries prognostic significance, but the 2 cm cut off in the staging system is subjective