title: A case of immunohistochemical false positive staining caused by incompatibility between a CD4 antibody and an autostainer.
abstract: Precise immunophenotyping of tumor cells by immunohistochemistry is complementary to morphological examination. It is critical for the correct histopathological diagnosis of lymphomas. In this paper, we report a case of T-cell lymphoma whose histopathological diagnosis was confounded by an immunohistochemical pitfall: a false positive caused by incompatibility between an antibody and an autostainer. In this case, based on CD4 immunohistochemistry of the affected lymph nodes, the T-cell lymphoma was diagnosed as CD4-positive at the onset, while it appeared discordantly to be CD4-negative at the second relapse. We noticed that CD4 antibodies and autostainers of different suppliers (designated as suppliers X and Y) were used in an unqualified combination in immunohistochemistry at the onset: that is, the combination of an antibody supplied by X and an autostainer supplied by Y (designated as X-Y combination) was used at the onset. On the other hand, the Y-Y combination was at the second relapse. At the second relapse, flow cytometry of the affected lymph node showed infiltration of CD4-negative T-cell lymphoma. We reasoned that CD4 immunonegativity obtained by the Y-Y combination at the second relapse was specific, while CD4 immunopositivity by the X-Y combination at the onset was false positive. Immunohistochemical reexamination of the lymph node at the onset proved to be CD4-negative by not only the Y-Y but also X-X combinations, confirming our final diagnosis of nodal relapse of CD4-negative T-cell lymphoma. This case illustrates the importance of using compatible combinations of antibodies and autostainers in diagnostic immunohistochemistry.
authors.affiliation: Department of Surgical Pathology, Hyogo College of Medicine Hyogo, Japan.
authors.forename: Ikuo
authors.initials: I
authors.lastname: Matsuda
authors.affiliation: Department of Gastroenterology, Takarazuka Municipal Hospital Hyogo, Japan ; Second Department of Internal Medicine, National Defense Medical College Saitama, Japan.
authors.forename: Nao
authors.initials: N
authors.lastname: Sugihara
authors.affiliation: Department of Gastroenterology, Takarazuka Municipal Hospital Hyogo, Japan.
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Yunokizaki
authors.affiliation: Department of Gastroenterology, Takarazuka Municipal Hospital Hyogo, Japan.
authors.forename: Takashi
authors.initials: T
authors.lastname: Abe
authors.affiliation: Department of Surgical Pathology, Hyogo College of Medicine Hyogo, Japan.
authors.forename: Seiichi
authors.initials: S
authors.lastname: Hirota
mesh_terms: D000906:Antibodies; D015704:CD4 Antigens / Q000032:analysis*; D005189:False Positive Reactions; D006801:Humans; D007150:Immunohistochemistry / Q000295:instrumentation* / Q000379:methods; D016130:Immunophenotyping; D016399:Lymphoma, T-Cell / Q000175:diagnosis* / Q000276:immunology; D008297:Male; D008875:Middle Aged; D013194:Staining and Labeling / Q000295:instrumentation / Q000379:methods
chemical_list: D000906:Antibodies; D015704:CD4 Antigens
keywords: CD4; Immunohistochemistry; T-cell lymphoma; autostainer; false positive