Why does it matter if a lymphoma is cd20 positive?

CD-20+ matters. Greatly. 1. Defiens as a b-cell lympoma; 2. High prospect that anti-cd-20 anitbody alone or conhugated with yttrium-90 or iodine 125 will cause response/salvage/even cure. Also, these will *not* work with cd-20 negative tumors.
Treatment... Certain nuclear medicine treatments for lymphoma such as zevalin and Bexxar (tositumomab) are used for refractory or relapsed cd20 positive non-hodgkin's lymphoma.
Therapy. Lymphomas that are cd20 positive can be treated with medications that attack the cd20 protein on the surface of the cell. The most commonly used in the United States is rituximab.