Stages and Grades of Eye cancer

Executive Summary

The stages of eye cancer help determine the tumor’s location and metastasis. The staging system of eye cancer uses diagnostic tests. A TNM staging system is used to identify the different stages of eye cancer. There are four stages of eye cancer – stages I through IV (one through four). T for an iris melanoma is described differently than T for ciliary body and choroidal melanomas in eye cancer. N and M are the same for iris, choroidal, and ciliary body melanomas. Cancer’s grade helps the doctor predict how quickly cancer will spread. In general, the lower the tumor’s grade, the better the prognosis. The biopsy helps identify the types of cells in the tumor, known as histopathology. Three histopathology patterns are present in the tumors involving spindle cell melanoma, epithelioid melanoma, and mixed cell melanoma. The eye tumors are given a grade (G) to describe the composition of their cells involving GX, G1, G2, and G3. Staging of eye cancer includes four stages involving stage I, stage II (IIA, IIB), stage III (IIIA, IIIB, IIIC), and stage IV. Instead of describing the TNM system, eye tumors are classified by guidelines from the Collaborative Ocular Melanoma Study (COMS) involving small, medium, and large with variations in diameter and height.

Stages and Grades of Eye Cancer

Staging is the procedure of determining where the tumor is located, whether it has spread or not, and how it grows which is used to find the stages of eye cancer ^​1​.

TNM staging system

The TNM system is the tool doctors use to describe the stage of Eye cancer. 

• T is for tumour – How large the tumour is and where is its location
• N is for nodes – Has cancer spread to lymph nodes, and if so, where and how many?
• M is for metastasis – Whether cancer has metastasized to other parts of the body distant from the eye.

The results are combined to check the stage of eye cancer for each person. There are four stages of eye cancer – stages I through IV (one through four). T for an iris melanoma is described differently than T for ciliary body and choroidal melanomas in eye cancer. N and M are defined the same for iris, choroidal, and ciliary body melanomas.

Tumour (T)

The below classifications are the same for any intraocular melanoma:

TX – The primary tumour cannot be evaluated.

T0 – There is no tumour in the eye.

Iris melanoma

An iris tumour is T1, T2, T3, or T4. Some stages of eye cancer are classified into smaller groups that help describe the tumour in even more detail.

• T1 – The tumour is restricted to the iris.
• T1a – The tumour is in one quadrant (one-fourth) or less of the iris.
• T1b – The tumour is in more than one quadrant of the iris.
• T1c – The tumour is only in the iris, but there is melanomalytic glaucoma. This means that a buildup of specific cells in the eye blocks fluid flow in the eye, causing pressure.
• T2 – The tumour has joined or grown into the ciliary body or choroid.
• T2a – The tumour has joined or grown into the ciliary body or choroid with melanomalytic glaucoma.
• T3 – The tumour has joined or grown into the ciliary body or choroid and extends to the sclera.
• T3a – The tumour has joined or grown into the ciliary body or choroid and extends to the sclera associated with melanomalytic glaucoma.
• T4 – The tumour has spread to the outside of the eyeball, the optic nerve, or to the eye socket. This is called extraocular extension.
• T4a – The tumour has spread less than 5 millimetres (mm) outside the eye.
• T4b – The tumour has spread more than 5 mm outside the eye.

Ciliary body and choroid melanoma

A tumor in the ciliary body and choroid is also classified as T1, T2, T3, or T4 based on the tumor size, measured in optic disc diameters or mm ^​2​. The tumor is measured for width and height (also called thickness). According to the table below, a tumor is classified based on its width and height.

The doctors may use and refer to a category, even more than the stages of eye cancer. This is because the thickness and size of the tumour (the T) are most important for finding out a patient’s prognosis.

• T1 – The tumour is size category.
• T1a – The tumour is size category one and does not involve the ciliary body or other eye parts.
• T1b – The tumour is category one and involves the ciliary body.
• T1c – The tumour is size category one that does not involve the ciliary body. But, there is a tiny area (5 mm or less in diameter) of visible spread beyond the eyeball. This is called the extraocular spread.
• T1d – The tumour is a size category one that involves the ciliary body with an extraocular spread of less than 5 mm.
• T2 – The tumour is size category 2.
• T2a – The tumour is size category two and does not involve the ciliary body or other eye parts.
• T2b – The tumour is category two and involves the ciliary body.
• T2c – The tumour is size category two that does not involve the ciliary body. But, there is a tiny area (5 mm or less in diameter) of visible spread beyond the eyeball.
• T2d – The tumour is size category two that involves the ciliary body with extraocular spread less than 5 mm.
• T3 –The tumour is size category 3.
• T3a –The tumour is category three and does not involve the ciliary body or other eye parts.
• T3b – The tumour is category three and involves the ciliary body.
• T3c – The tumour is size category three that does not involve the ciliary body. But, there is a tiny area (5 mm or less in diameter) of visible spread beyond the eyeball.
• T3d-The tumour is size category three, involving the ciliary body with an extraocular spread of less than 5 mm.
• T4 – The tumour is size category 4.
• T4a – The tumour is category four and does not involve the ciliary body or other eye parts.
• T4b – The tumour is category four and involves the ciliary body.
• T4c – The tumour is size category four that does not involve the ciliary body. But, there is a tiny area (5 mm or less in diameter) of visible spread beyond the eyeball.
• T4d – The tumour is size category four, involving the ciliary body with an extraocular spread of less than 5 mm.
• T4e – The tumour is any size category with an extraocular spread of more than 5 mm in diameter.

Node (N)

N is described the same for the iris, ciliary body, and choroid melanomas.

• NX – The regional lymph nodes cannot be evaluated.
• N0 (N plus zero) – There is no regional lymph node metastasis.
• N1 – There is regional lymph node metastasis.

Metastasis (M)

M is described as the ciliary body, iris, and choroidal melanomas.

• MX- Distant metastasis cannot be evaluated.
• M0 (M plus zero)- There is no distant metastasis.
• M1- There is metastasis to other parts of the body.
• M1a – There is metastasis to other parts of the body, and the most significant metastasis is 3 centimetres (cm) or less in diameter.
• M1b- There is metastasis to other parts of the body, and the most significant metastasis is between 3.1 cm and 8 cm in diameter.
• M1c- There is metastasis to other body parts, and the most significant metastasis is larger than 8 cm in diameter.

Eye Cancer Grade and Histopathology

Doctors describe eye cancer by its grade (G), which tells how much cancer cells look like healthy cells when viewed using a microscope. The doctor compares the cancerous tissue with healthy tissue. Healthy tissue contains various types of cells grouped.

If cancer looks similar to healthy tissue and contains different cell groupings, it is differentiated or low-grade tumors. If the cancerous tissue looks much different from healthy tissue, it is poorly differentiated or a high-grade tumor.

Cancer’s grade helps the doctor predict how quickly cancer will spread. In general, the lower the tumor’s grade, the better the prognosis.

After a biopsy or when the tumor is surgically removed, doctors may look at the types of cells in the tumor; this is called histopathology. Three types of histopathology patterns may be present in the tumor ^​3​:

• Spindle cell melanoma (the cells are long and tapered at the ends)
• Epithelioid melanoma (the cells are oval-shaped)
• Mixed cell melanoma (both spindle and epithelioid)

Generally, a tumor made up of spindle cells has a better prognosis than a tumor made up of epithelioid cells. The tumor is given a grade (G) to describe the composition of its cells. A lower grade of eye cancer usually indicates a better prognosis than a higher grade.

GX – Grade cannot be evaluated

G1 – A spindle cell melanoma

G2 – A mixed cell melanoma

G3 – An epithelioid melanoma

Eye cancer stages grouping

Doctors assign the eye cancer stages by combining the T, N, M, and G classifications.

Stage I – The tumour is size category one and does not involve the ciliary body or other eye parts, nor has it spread to the regional lymph nodes or other areas of the body (T1a, N0, M0).

Stage IIA – The tumor is either a size category one that may or may not involve the ciliary body, with or without extraocular extension or a size category two that does not include the ciliary body. There is no spread to the regional lymph nodes or other body areas (T1b, T1c, T1d, or T2a; N0, M0).

Stage IIB – The tumor is a size category two that involves the ciliary body but has not spread outside the eyeball. It is a size category three that has not spread to the ciliary body or eyeball. It hasn’t spread to the regional lymph nodes or other body areas (T2b or T3a; N0, M0).

Stage IIIA – Stage IIIA describes any one of these conditions:

• A tumor of the size category 2 with extraocular spread to a diameter of 5 mm or less, with or without ciliary body involvement that hasn’t spread to the lymph nodes or other body parts(T2c or T2d, N0, M0)
• A tumor of the size category three that may or may not include the ciliary body, with or without extraocular spread to a diameter of 5 mm or less, but hasn’t spread to the lymph nodes or other parts of the body (T3b or T3c, N0, M0)
• A tumor of the size category four that does not involve the ciliary body and has not spread to the lymph nodes or other body parts (T4a, N0. M0)

Stage IIIB – Stage IIIB describes any one of these conditions:

• The tumor is a category 3 with ciliary body involvement and extraocular spread that has not spread to the lymph nodes or other body parts (T3d, N0, M0).
• The tumor is a category 4 with or without ciliary body involvement that may have spread outside the eyeball. It hasn’t spread to the regional lymph nodes or other body areas (T4b or T4c, N0, M0).

Stage IIIC – The tumor is a size category four that involves the ciliary body and has spread outside the eyeball. However, it has not spread to the regional lymph nodes or other areas of the body (T4d or T4e; N0, M0).

Stage IV – This stage describes a tumor of any size that has spread to the lymph nodes or other body parts outside of the eye (any T, N1, M0; or, any T, any N, M1).

COMS Tumor Classifications

Instead of describing the TNM system, eye tumors can be classified by these guidelines from the Collaborative Ocular Melanoma Study (COMS).

• Small: 5 mm to 16 mm in diameter and 1 mm to 3 mm in height 
• Medium: Not more than 16 mm in diameter and 3.1 mm to 8 mm in height 
• Large: More than 16 mm in diameter and more than 8 mm in height 

Recurrence of Eye Cancer

Cancer that has come back after treatment is called recurrent cancer. It may come back in the eye or another part of the body. If eye cancer returns, the doctor performs another round of tests to know the extent of the recurrence and stages of eye cancer. These tests and scans are mainly similar to those done at the original diagnosis.

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