Cervical cancer is divided into stages to help doctors understand how far the cancer has spread and to guide treatment decisions. The stages are determined based on several factors, including the size of the tumor, whether cancer has spread to nearby lymph nodes or other organs, and if it has metastasized (spread) to distant parts of the body.

Stage 0 (Carcinoma in situ): At this early stage, cancer cells are found only in the surface layer of the cervix and have not invaded deeper tissues. It is often called "pre-cancer" because it hasn't spread beyond the surface.

Stage I: Cancer is confined to the cervix and has not spread to nearby lymph nodes or other organs. Stage I is further divided into:

Stage IA: Cancer is microscopic and can only be seen under a microscope.
Stage IB: Cancer is visible without a microscope and may be larger than 4 centimeters (cm).

Stage II: Cancer has spread beyond the cervix but is still within the pelvic area. Stage II is further divided into:
Stage IIA: Cancer has spread to the upper two-thirds of the vagina but not to the walls of the pelvis.
Stage IIB: Cancer has spread to the tissues around the cervix but not to the pelvic wall or the lower part of the vagina.

Stage III: Cancer has spread to the lower part of the vagina or the walls of the pelvis, and may also affect nearby lymph nodes. Stage III is further divided into:
Stage IIIA: Cancer has spread to the lower part of the vagina but not to the walls of the pelvis.
Stage IIIB: Cancer has spread to the pelvic wall or causes kidney problems.

Stage IV: Cancer has spread to nearby organs outside the pelvic area or to distant parts of the body. Stage IV is further divided into:
Stage IVA: Cancer has spread to nearby organs, such as the bladder or rectum.
Stage IVB: Cancer has spread to distant parts of the body, such as the lungs, liver, or bones.

Determining the stage of cervical cancer usually involves a combination of physical examination, imaging tests (such as CT scans or MRIs), and sometimes, surgical procedures to remove lymph nodes for examination. Understanding the stage of cervical cancer helps doctors plan the most appropriate treatment approach for each individual patient.