Reese-Ellsworth grouping system

Definition of Reese-Ellsworth Classification System

Reese-Ellsworth Classification System

(rees-ELZ-wurth KLA-sih-fih-KAY-shun SIS-tem)
The Reese-Ellsworth classification system for intraocular retinoblastoma is as follows: Group I retinoblastoma (very favorable for maintenance of sight): (1) solitary tumor, smaller than 4 disc diameters (DD), tumor is at or behind the equator; or (2) multiple tumors, none larger than 4 DD, all tumors are at or behind the equator. Group II retinoblastoma (favorable for maintenance of sight): (1) solitary tumor, 4 to 10 DD, tumor is at or behind the equator; or (2) multiple tumors, 4 to 10 DD, all tumors are behind the equator. Group III retinoblastoma (possible maintenance of sight): (1) any lesion anterior to the equator; or (2) solitary tumor, larger than 10 DD, tumor is behind the equator. Group IV retinoblastoma (unfavorable for maintenance of sight): (1) multiple tumors, some larger than 10 DD; or (2) any lesion extending anteriorly to the ora serrata. Group V retinoblastoma (very unfavorable for maintenance of sight): (1) massive tumors involving more than one-half of the retina; or (2) vitreous seeding.

Source: NCI Dictionary of Cancer Terms