FIGO's staging classification for cancer of the ovary, fallopian tube, and peritoneum: abridged republication

Jaime Prat

doi:10.3802/jgo.2015.26.2.87

Over the past quarter of a century, several scientific developments have challenged traditional concepts in ovarian cancer. First, it was recognized that ovarian cancer is not a homogeneous disease, but rather a group of diseases-each with different morphology and biological behavior. Approximately 90% of ovarian cancers are carcinomas (malignant epithelial tumors) and, based on histopathology, immunohistochemistry, and molecular genetic analysis, at least five main types are currently distinguished: high-grade serous carcinoma (HGSC, 70%); endometrioid carcinoma (EC,10%); clear-cell carcinoma (CCC,10%); mucinous carcinoma (MC, 3%); and low-grade serous carcinoma (LGSC, <5%) [1,2]. These tumor types (which account for 98% of ovarian carcinomas) can be reproducibly diagnosed by light microscopy and are inherently different diseases, as indicated by differences in epidemiologic and genetic risk factors; precursor lesions; patterns of spread; and molecular events during oncogenesis, response to chemotherapy, and prognosis [2,3]. Much less common are malignant germ cell tumors and potentially malignant sex cord-stromal tumors. The biomarker expression profile within a given histotype is consistent across stages. Ovarian cancers differ primarily based on histologic type.

In the era of personalized cancer medicine, reproducible histopathologic diagnosis of tumor cell type is a sine qua non for successful treatment. Different tumor histotypes respond differently to chemotherapy. The International Federation of Gynecology and Obstetrics (FIGO) Committee on Gynecologic Oncology unanimously agreed that histologic type should be designated at staging.

The finding of high-grade serous tubal intraepithelial carcinoma (STIC), in patients with BRCA mutation undergoing risk-reducing salpingo-oophorectomy (RRSO)[4] also influenced the new FIGO staging. Although STIC is capable of metastasizing and, therefore, cannot be considered a true carcinoma in situ , compelling evidence for a tubal origin of BRCA-positive HGSC has accumulated over the past decade [5,6]. The relative proportion of HGSCs of ovarian and tubal derivation is unknown, mainly because tumor growth in advanced-stage cancers conceals the primary site. Even in cases involving BRCA mutation, evidence of a tubal origin of HGSCs is incomplete and a multicentric origin of these tumors cannot be excluded.

The process of the proposed changes to the staging of ovarian, fallopian tube, and primary peritoneal cancer started three years ago under the leadership of the Chair of the FIGO Committee on Gynecologic Oncology, Professor Lynette Denny. The proposal was sent to all relevant gynecologic oncology organizations and societies worldwide. The new staging was reached by consensus of those participating in the FIGO meeting held in Rome, Italy, on October 7, 2012 and approved two weeks later.

The following is the consensus agreement that resulted from these efforts and represents new criteria for staging of these gynecologic cancer (Table 1).

MAIN CHANGES

The primary site (i.e., ovary, fallopian tube, or peritoneum) should be designated where possible. In some cases, it might not be possible to delineate the primary site clearly; such cases should be listed as "undesignated". The histologic type should be recorded.

Stage I ovarian or fallopian tube cancer is confined to the ovaries or the fallopian tubes and peritoneal fluid/washings. Tumor rupture, surface involvement by tumor cells or presence of malignant cells in the ascites or peritoneal washings warrants a stage of IC. It is not possible to have stage I peritoneal cancer.

Stage II ovarian cancer comprises a small and heterogeneous group making up less than 10% of ovarian cancers. It is defined as extension or metastasis to extraovarian/extratubal pelvic organs and may include curable tumors that have directly extended to adjacent organs but have not yet metastasized, as well as tumors that have seeded the pelvic peritoneum by metastasis and, therefore, have a poor prognosis. The Committee felt that subdividing this small category further into IIB1 and IIB2 (i.e., microscopic and macroscopic pelvic peritoneal metastases) was not based on evidence/biology. All stage II disease is treated with adjuvant chemotherapy, so subclassification is not essential. Also, the old substage IIC (i.e., IIA or IIB but with tumor on surface, capsule ruptured, or ascites or positive peritoneal washing) was considered redundant and eliminated.

Most ovarian cancers are HGSCs that usually present in stage III, with the vast majority (84%) stage IIIC [7]. These tumors characteristically spread along peritoneal surfaces involving both pelvic and abdominal peritoneum. Less than 10% of ovarian carcinomas extend beyond the pelvis with exclusively retroperitoneal lymph node involvement. Evidence in the literature indicates that these cases have a better prognosis than that of tumors with abdominal peritoneal involvement [8,9,10,11,12,13,14]. The new staging includes a revision of stage III patients and assignment to stage IIIA1 based on spread to the retroperitoneal lymph nodes without intraperitoneal dissemination. Stage IIIA1 is further subdivided into IIIA1(i) (metastasis ≤10 mm in greatest dimension) and IIIA1(ii) (metastasis >10 mm in greatest dimension), even if there are no retrospective data supporting quantification of the size of metastasis in IIIA1. Involvement of retroperitoneal lymph nodes must be proven cytologically or histologically.

Stage IV is defined as distant metastasis and includes patients with parenchymal liver/splenic metastases and extra-abdominal metastases; 12% to 21% of patients present with stage IV disease [7]. Extension of tumor from omentum to spleen or liver (stage IIIC) should be differentiated from isolated parenchymal metastases (stage IVB).

ACKNOWLEDGMENTS

¹Committee members: H. Belhadj (Switzerland), J. Berek (USA), A. Bermudez (Argentina), N. Bhatla (India), J. Cain (USA), L. Denny (Chair; South Africa), K. Fujiwara (Japan), N. Hacker (Australia), E. Åvall-Lundqvist (Sweden), D. Mutch (USA), F. Odicino (Italy), S. Pecorelli (Italy), J. Prat (Spain), M. Quinn (Co-chair; Australia), M.A-F. Seoud (Lebanon), S.K. Shrivastava (India).

Notes

This article is an abridged version of the staging classification published in the International Journal of Gynecology and Obstetrics in January 2014. Please cite the original article as: Prat J; FIGO Committee on Gynecologic Oncology. Staging classification for cancer of the ovary, fallopian tube, and peritoneum. Int J Gynecol Obstet 2014;124(1):1-5. Copyright Elsevier (2013)

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