How are eye cancers staged?

Staging is the process of finding out how far a cancer has spread. The stage (extent) of an eye cancer is one of the most important factors in selecting treatment options and estimating a patient's outlook for recovery and survival (prognosis).

The stage of a cancer is determined from the results of eye exams, imaging tests (ultrasound, CT or MRI scan, etc.) and other tests, which are described in the section, "How is eye cancer diagnosed?"

A staging system is a standardized way for the cancer care team to summarize information about how far a cancer has spread. The most common systems used to describe the stages of eye melanomas are the American Joint Committee on Cancer (AJCC) TNM system and the system used by the Collaborative Ocular Melanoma Study (COMS) group.

AJCC TNM staging system for melanoma of the eye

The TNM system is based on 3 key pieces of information:

• T describes the size of the primary tumor and/or whether it has invaded into nearby structures.
• N describes whether the cancer has spread to nearby (regional) lymph nodes (bean-sized collections of immune system cells located throughout the body).
• M indicates whether the cancer has metastasized (spread) to other organs of the body. (The most common site of eye melanoma spread is the liver.)

Numbers or letters appear after T, N, and M to provide more details about each of these factors:

• The numbers 0 through 4 indicate increasing severity. Lower case letters after the numbers divide these groups further.
• The letter X means "cannot be assessed" because the information is not available.

Most eye melanomas start in the uvea, which includes the iris, ciliary body, and choroid (see "What is eye cancer?"). The T categories for iris melanomas are different from the T categories for ciliary body and choroidal melanomas. But the N and M categories are the same for melanomas in all 3 parts of the uvea.

T categories for iris melanoma

TX: The main (primary) tumor cannot be assessed; information not known.

T0: No evidence of a primary tumor.

T1: Tumor is only in the iris.

• T1a: The tumor is only in the iris and touches 1/4 or less of the iris.
• T1b: The tumor is only in the iris and touches more than 1/4 of the iris.
• T1c: The tumor is only in the iris and is causing an increase in the eye pressure (glaucoma).

T2: Tumor has grown into the ciliary body or choroid (or both).

• T2a: Tumor has grown into the ciliary body and/or choroid and is causing glaucoma.

T3: Tumor has grown into the ciliary body and/or choroid and into the sclera.

• T3a: Tumor has grown into the ciliary body and/or choroid and into the sclera and is causing glaucoma.

T4: Tumor extends outside the eyeball.

• T4a: The part of the tumor that is outside the eyeball is 5 millimeters (mm) — about 1/5 of an inch — or less across in size.
• T4b: The part of the tumor that is outside the eyeball is greater than 5 mm (about 1/5 of an inch) across in size.

T categories for ciliary body and choroidal melanoma

TX: The main (primary) tumor cannot be assessed; information not known.

T0: No evidence of a primary tumor.

T1: Tumor size is either:

• No more than 3 mm deep and no more than 12 mm across, OR
• From 3.1 to 6 mm deep and no more than 9 mm across

T1a: The tumor is T1 in size and is not growing into the ciliary body or growing outside the eyeball.

T1b: The tumor is T1 in size and is growing into the ciliary body.

T1c: The tumor is T1 in size and is not growing into the ciliary body but is growing outside of the eyeball. The part of the tumor that is outside the eyeball is 5 mm (about 1/5 of an inch) or less across in size.

T1d: The tumor is T1 in size and is growing into the ciliary body. It is also growing outside of the eyeball. The part of the tumor that is outside the eyeball is 5 mm (about 1/5 of an inch) or less across in size.

T2: Tumor size is one of the following:

• No more than 3 mm deep and from 12.1 to 18 mm across.
• From 3.1 to 6 mm deep and 9.1 to 15 mm across
• From 6.1 to 9 mm deep and no more than 12 mm across

T2a: The tumor is T2 in size and is not growing into the ciliary body or growing outside the eyeball.

T2b: The tumor is T2 in size and is growing into the ciliary body.

T2c: The tumor is T2 in size and is not growing into the ciliary body but is growing outside of the eyeball. The part of the tumor that is outside the eyeball is 5 mm (about 1/5 of an inch) or less across in size.

T2d: The tumor is T2 in size and is growing into the ciliary body. It is also growing outside of the eyeball. The part of the tumor that is outside the eyeball is 5 mm (about 1/5 of an inch) or less across in size.

T3: Tumor size is one of the following:

• From 3.1 to 6 mm deep and between 15.1 and 18 mm across
• From 6.1 to 9 mm deep and between 12.1 and 18 mm across
• From 9.1 to 12 mm deep and 18 mm or less across
• From 12.1 to 15 mm deep and 15 mm or less across

T3a: The tumor is T3 in size and is not growing into the ciliary body or growing outside the eyeball.

T3b: The tumor is T3 in size and is growing into the ciliary body.

T3c: The tumor is T3 in size and is not growing into the ciliary body but is growing outside of the eyeball. The part of the tumor that is outside the eyeball is 5 mm (about 1/5 of an inch) or less across in size.

T3d: The tumor is T3 in size and is growing into the ciliary body. It is also growing outside of the eyeball. The part of the tumor that is outside the eyeball is 5 mm (about 1/5 of an inch) or less across in size.

T4: Tumor size is one of the following:

• Greater than 15 mm deep and any width
• Greater than 18 mm across and any depth
• Between 12.1 and 15 mm deep and between 15.1 and 18 mm across

T4a: The tumor is T4 in size and is not growing into the ciliary body or growing outside the eyeball.

T4b: The tumor is T4 in size and is growing into the ciliary body.

T4c: The tumor is T4 in size and is not growing into the ciliary body but is growing outside of the eyeball. The part of the tumor that is outside the eyeball is 5 mm (about 1/5 of an inch) or less across in size.

T4d: The tumor is T4 in size and is growing into the ciliary body. It is also growing outside of the eyeball. The part of the tumor that is outside the eyeball is 5 mm (about 1/5 of an inch) or less across in size.

T4e: The tumor can be any size. It is growing outside the eyeball and the part of the tumor that is outside the eyeball is greater than 5 mm across.

N categories for iris, ciliary body, and choroidal melanomas

NX: Lymph nodes cannot be assessed.

N0: Cancer has not spread to nearby lymph nodes.

N1: Cancer has spread to nearby lymph nodes.

M categories for iris, ciliary body, and choroidal melanomas

M0: Cancer has not spread to distant parts of the body.

M1: Cancer has spread to distant parts of the body.

M1a: The largest area of cancer spread is 3 centimeters (cm) — a little over an inch — across or smaller.

M1b: The largest area of cancer spread is between 3.1 and 8 cm across (8 cm is a little over 3 inches).

M1c: The largest area of cancer spread is 8.1 cm or more across.

Stage grouping

To assign an overall stage, information about the T, N, and M categories is combined by a process called stage grouping. The stages are described by Roman numerals from I (the least advanced) to IV (the most advanced). Some stages are further divided with letters.

COMS staging of melanoma of the eye

The TNM system is very detailed, but many doctors use the simpler staging system devised by the Collaborative Ocular Melanoma Study (COMS) group, which has done most of the clinical research on how to treat intraocular melanoma. This system divides eye melanomas into small, medium, and large.

Staging of intraocular lymphoma

Intraocular lymphoma does not have a unique staging system. These cancers may be staged with the system used for other non-Hodgkin lymphomas, which is described in our separate document, Non-Hodgkin Lymphoma.

Treatment options are generally based on the type of lymphoma, as well as on whether the lymphoma is limited to the eye or is also in other areas of the body.

Because eye lymphoma is rare, accurate survival statistics for this cancer are hard to find. In one review of patients whose lymphoma was confined to the eye, about half of the patients were still alive 5 years after diagnosis. Unfortunately, in many cases the lymphoma has already reached the brain at the time of diagnosis, in which case the outlook is not as good.