The new FIGO staging system for ovarian, fallopian tube, and primary peritoneal cancer

Recent molecular research has revolutionized the understanding of ovarian cancer. It is now non-controversial that the term ovarian cancer summarizes a heterogenous group of malignant epithelial tumors. Findings of large clinical trials investigating surgical and systemic therapeutic approaches have defined the most important prognostic parameters. Therefore, the oncology committee of FIGO, headed by the South African gynecologic oncologist Lynette Denny, took the effort to revise the FIGO classification of ovarian cancer that was implemented in 1988.

The recent publication of Jaime Prat describing the new FIGO classification is summarized. The major changes compared to the hitherto existing classification from 1988 are presented.

The primary anatomy is now documented (ov for ovarian, ft for fallopian tube, p for peritoneal, X for not assessed). The histological subtype is also documented (HGSC for high-grade serous carcinoma, LGSC for low-grade serous carcinoma, MC for mucinous carcinoma, CCC for clear cell carcinoma, and EC for endometrioid carcinoma). There is no stage I peritoneal cancer. Stage IC is subdivided into intraoperative rupture (IC1), pre-operative rupture (IC2), and malignant ascites or peritoneal washings (IC3). Due to its anatomic position within the pelvis, metastasis to the sigmoid colon is considered stage II. Former stage IIC has been erased. Stage IIIA1 and IIIA2 have been defined for intra-pelvic tumor with metastasis to retro-peritoneal lymph nodes up to 1 cm (IIIA1) or larger than 1 cm (IIIA2). With this, some of the former stage IIIC cases become IIIA and some IIIB, respectively. Involvement of retroperitoneal lymph nodes must be proven cytologically or histologically. Stage IV has been subdivided into IVA (malignant pleural effusions) and IVB (parenchymal metastases and/or extra-abdominal metastases including tumors in inguinal lymph nodes or lymph nodes outside of the abdominal cavity, umbilical tumor deposit, and transmural bowel infiltration (with mucosal involvement).

The new FIGO classification takes into account the recent findings on the origin, pathogenesis, and prognosis of different ovarian cancer subtypes, summarizes groups of tumors pragmatically, and implies a reproducible and stage-dependent therapeutical approach.