Neuroblastoma is classified using cancer staging, which is a process that determines how far a cancer has spread. Staging helps in two main ways:

1. It helps in planning the most appropriate therapy
2. It helps predict possible outcomes such as five-year survival, if treatment is or is not administered

Neuroblastoma is staged based on:

• Physical examination
• Imaging studies
• Biopsy or evaluation of the cellular structure and features of the tumor

Examples of the staging and systems of used include the International Neuroblastoma Staging System (INSS) for clinical staging and the International Neuroblastoma Risk Group Staging System (INRGSS).

International Neuroblastoma Staging System (INSS)

This is the most common staging system to be used since the mid-1990s. Under this system, the stages of neuroblastoma are defined as follows:

Stage 1 - Localized cancer that has stayed in the area where it originated. The cancer is on one side of the body. All of the visible tumor was removable through surgery. Neuroblastoma cells are not present in lymph nodes outside of the tumor.

Stage 2A - The cancer is still confined to the same area on one side of the body but not all visible tumor could be removed with surgery. Neuroblastoma cells are still not present in lymph nodes outside of the tumor.

Stage 2B - The cancer is on one side of the body but could not be completely removed with surgery. Neuroblastoma cells are present in nearby lymph nodes outside of the tumor. Lymph nodes elsewhere or on the other side of the body, however, do not contain tumor cells.

The cancer is still confined to site of origin on one side of body but has spread to nearby lymph nodes on the other side of the bodyStage 3 - The cancer has not spread to distant parts of the body but one of the following applies:

• Not all the cancer can be removed by surgery and has passed the midline (spine) to the other side of the body. There may or may not be nearby involvement of lymph nodes.
• The cancer is present in the central part of the body and is spreading to both sides, either though nearby lymph nodes or directly, and cannot be removed by surgery.

Stage 4 - The cancer spreads to far reaching sites such as the liver, bone marrow, skin, distant lymph nodes and other organs.

Stage 4S - Also called special neuroblastoma, this stage affects children aged under one year. The cancer is localized and confined to one side. It may have spread to lymph nodes on the same side and to the liver, skin and/or bone marrow.

Recurrent - Return of the cancer after successful treatment, either in the same area or another part of the body

International Neuroblastoma Risk Group Staging System (INRGSS)

The INRGSS uses a similar system to INSS but does not use the results of surgery as part of the basis for classification, focusing only on imaging studies, examinations and biopsies. The INGRSS has 4 stages:

L1 - Localized tumor that has not spread from where it began, does not involve any vital structure and is confined to a single compartment such as the abdomen or chest.

L2 - A tumor that has not grown far from its site of origin but involves at least 1 vital structure (eg, grown into a nearby organ or around blood vessels).

M - Tumor that has spread (metastasized) to a distant part of the body

MS - Tumor in children less than 18 months of age that has spread only to bone marrow, skin or liver.