There are several staging systems for retinoblastoma. For treatment, retinoblastoma is classified as intraocular (within the eye) or extraocular (outside the eye).
The following stages are used for retinoblastoma:
In intraocular retinoblastoma, cancer is found in the eye and may be only in the retina or may also be in other parts of the eye such as the choroid, ciliary body, or part of the optic nerve. Cancer has not spread to tissues around the outside of the eye or to other parts of the body.
In extraocular retinoblastoma, cancer has spread beyond the eye. It may be found in tissues around the eye (orbital retinoblastoma) or it may have spread to the central nervous system (brain and spinal cord) or to other parts of the body such as the bone marrow or lymph nodes (metastatic retinoblastoma).
There are three ways that cancer spreads in the body.
The three ways that cancer spreads in the body are:
- Through tissue. Cancer invades the surrounding normal tissue.
- Through the lymph system. Cancer invades the lymph system and travels through the lymph vessels to other places in the body.
- Through the blood. Cancer invades the veins and capillaries and travels through the blood to other places in the body.
When cancer cells break away from the primary (original) tumor and travel through the lymph or blood to other places in the body, another (secondary) tumor may form. This process is called metastasis. The secondary (metastatic) tumor is the same type of cancer as the primary tumor. For example, if breast cancer spreads to the bones, the cancer cells in the bones are actually breast cancer cells. The disease is metastatic breast cancer, not bone cancer.