The Reese-Ellsworth classification system was developed by two physicians as a method to predict prognosis of eyes treated by methods which save or preserve the eye. The higher the Group number in the system, the poorer the chance is of saving the eye.

Reese-Ellsworth Classification for Retinoblastoma

Group I

a. Solitary tumor, less than 4 disc diameters in size, at or behind the equator.
b. Multiple tumors, none over 4 disc diameters in size, all at or behind the equator.

Group II

a. Solitary tumor, 4 to 10 disc diameters in size, at or behind the equator.
b. Multiple tumors, 4 to 10 disc diameters in size, all at or behind the equator.

Group III

a. Any lesion anterior to the equator.
b. Solitary tumor larger than 10 disc diameters in size behind the equator.

Group IV

a. Multiple tumors, some larger than 10 disc diameters.
b. Any lesion extending anterior to the ora serrata.

Group V

a. Massive tumors involving over half the retina.
b. Vitreous seeding. 

Recently, a staging system was developed to group retinoblastoma tumors confined to the eye and those tumors which spread outside of the eye and in other parts of the body. This system is referred to as the Abramson Staging System for Retinoblastoma.

Abramson Staging System for Retinoblastoma

1. Intraocular disease

a. Retinal tumors
b. Extension into choroid
c. Extension up to lamina cribrosa
d. Extension into sclera

2. Orbital disease

a. Orbital tumor

1. Suspicious (pathology of scattered episcleral cells)
2. Proven (biopsy-proven orbital tumor)

b. Local nodal involvement

3. Optic nerve disease

a. Tumor beyond lamina cribrosa but not up to cut section
b. Tumor at cut section of optic nerve

4. Intracranial metastasis

a. Positive CSF only
b. Mass CNS section

5. Hematogenous metastasis

a. Positive marrow/bone lesions
b. Other organ involvement

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