title: Loss of CD20 expression in relapsed lymphomas after rituximab therapy.
abstract: The response rate at relapse to rituximab in prior responders B-cell non-Hodgkin's lymphoma (NHL) patients is below 50%. Loss of CD20 expression after rituximab therapy may explain this secondary resistance. However, the frequency of CD20 negative relapses cannot be assessed since most patients that relapsed after rituximab therapy have not been re-biopsied. Here, we present two patients with CD20 positive low grade B-cell NHL that lost the cell surface and cytoplasmic expression at relapse after rituximab therapy. Our findings suggest that confirmation of CD20 expression on the malignant B cells is required whenever rituximab therapy is considered.
authors.affiliation: Departments of Pathology and Laboratory Medicine, Internal Medicine, American University of Beirut, Beirut, Lebanon. jh01@aub.edu.lb
authors.forename: Joud H
authors.initials: JH
authors.lastname: Haidar
authors.forename: Ali
authors.initials: A
authors.lastname: Shamseddine
authors.forename: Ziad
authors.initials: Z
authors.lastname: Salem
authors.forename: Yasser Abou
authors.initials: YA
authors.lastname: Mrad
authors.forename: Michel R
authors.initials: MR
authors.lastname: Nasr
authors.forename: Ghazi
authors.initials: G
authors.lastname: Zaatari
authors.forename: Ali
authors.initials: A
authors.lastname: Bazarbachi
mesh_terms: D000368:Aged; D000911:Antibodies, Monoclonal / Q000627:therapeutic use*; D058846:Antibodies, Monoclonal, Murine-Derived; D018951:Antigens, CD20 / Q000378:metabolism*; D002462:Cell Membrane / Q000276:immunology; D003593:Cytoplasm / Q000276:immunology; D005260:Female; D006801:Humans; D016393:Lymphoma, B-Cell / Q000276:immunology* / Q000628:therapy*; D008228:Lymphoma, Non-Hodgkin / Q000276:immunology / Q000628:therapy; D008875:Middle Aged; D012008:Recurrence; D000069283:Rituximab
chemical_list: D000911:Antibodies, Monoclonal; D058846:Antibodies, Monoclonal, Murine-Derived; D018951:Antigens, CD20; D000069283:Rituximab