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

Abstract

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). Table 1 2014 FIGO ovarian, fallopian tube, and peritoneal cancer staging system and corresponding TNM