CD20 expression (CD20-positive)

Overview

• Lymphoma: the stain is part of every diagnostic panel and is not repeated before each dose of rituximab, which is why loss at relapse is under-measured. Of 124 patients treated with rituximab-containing chemotherapy, 36 relapsed or progressed, 19 were rebiopsied and 5 of those, 26.3%, had become CD20-negative, with lower CD20 messenger RNA in the negative cells than in the positive cells from the same patient; all five died within a year (Hiraga 2009). The practical rule is to rebiopsy and restain before giving another CD20-directed drug. CD20 is not internalised, so it carries naked antibodies and T-cell engagers but no antibody-drug conjugate.