**4. Staging**

Ovarian cancer staging is surgical, being performed according to the International Federation of Gynecology and Obstetrics (FIGO) criteria [22]. CT or magnetic resonance imaging scans, although of limited impact for OC early diagnosis, allow to establish a surgery plan and to determine tumor irresectability criteria for 70–90% of all patients. The ability to detect peritoneal implants in both exams depends upon their location, size, and the presence of ascites. However, CT is the imaging modality of choice for OC staging, since it is indispensable for the preoperative evaluation to optimize maximal cytoreduction surgery or to help in the decision of neoadjuvant chemotherapy.

Ovarian cancer dissemination can occur through all known propagation routes, i.e., lymphatic, hematogenic, transcavitary, and contiguous. The transcavitary course is undoubtedly the most clinically relevant and, in the vast majority of cases, has an impact on the patient prognosis [23, 24]. The dissemination to the peritoneal cavity is an early phenomenon in the natural history of the disease, since the malignant cells follow the peritoneal fluid, flow concerning intra-abdominal pressure variations. Ovarian cells are characterized as anchoragedependent cells, meaning that they could only survive when adherent to the extracellular matrix or in contact with neighbor cells. However, when OC cells exfoliate into the peritoneal cavity, they can avoid anoikis (apoptosis process triggered by the loss of binding to the extracellular matrix) and survive even when isolated. Cancer cells in this state can survive and disseminate into the peritoneum, depositing accordingly to the passive flow distribution of peritoneal fluid, predominantly into the paracolic gutters, diaphragmatic surfaces, liver capsule, intestine surface, and omentum. The adhesion of malignant cells to the peritoneum precedes the local invasion and the secondary metastasis, namely to the pleural cavity by the transdiaphragmatic pores (Stage IV) [25]. The transcavitary route seems to be related to the OC cells predilection for the abdominal cavity (homing) rather than the deposition in other organs such as liver, lungs, brain, or bone (rarely in these latter two locations). The dissemination by contiguity is also important and of particular interest for organs like fallopian tubes, uterus, contralateral appendix and bladder, rectum, and pouch of Douglas. The iatrogenic route by contiguity, for example, to the abdominal wall is less frequent. Lymphatic dissemination is frequently observed when the disease is confined to the ovary, being found in almost 15% of FIGO I–II cases [26]. In fact, for a proper FIGO staging, lymphadenectomy is required, and the removal of bulky lymph nodes should be performed to achieve complete macroscopic resection. Although the systematic lymphadenectomy in advanced OC surgical management is still discussed, it has an impact in early disease stages not only to define FIGO staging but also to establish the need for adjuvant treatment, with a significant impact in survival [27, 28]. Blood dissemination is less frequent and usually occurs in advanced disease stages [23, 24].
