Most tumor of the ovaries start in the cells that line the ovaries (the epithelium); this is why this type of cancer is called epithelial carcinoma.

Epithelial carcinoma represents 85-90% of all cases, though we can also find tumors of the germinal cells and of the stroma (those these are uncommon).

The staging scale used is called FIGO, and it divides ovarian cancer into 4 stages:

Stage 1: The cancer only affects the ovaries.

• 1 a: when only one ovary is affected
• 1 b: two ovaries are affected
• 1 c: the tumor affects one or two ovaries but has ascites (fluid) with malignant cells, tumor on the surface of the ovary, or the ovary has burst.

Stage 2: The cancer has spread outside of the ovaries and affects the organs of the pelvis.

• 2 a: The cancer has spread to the fallopian tubes or the uterus
• 2 b: The cancer has spread to other structures of the pelvis such as the rectum or bladder.
• 2 c: Tumors in stage 2 a and 2 b that present ascites (fluid) with malignant cells.

Stage 3: The tumor has spread outside of the pelvis or into the lymph nodes.

• 3 a: Tumor located in the pelvis but with microscopic tumors in the abdomen. Lymph nodes are not affected.
• 3 b: Tumor located in the pelvis and abdomen (smaller than 2 cm) and without affecting the lymph nodes.
• 3 c: Tumor located in the pelvis and abdomen (larger than 2 cm) and affecting the lymph nodes.

Stage 4: The tumor has spread to far-away organs such as the liver, lung, and lymph nodes located outside of the abdomen.