Test Details: Immunohistochemical testing is carried out on biopsy/resected tissue specimen. This testing helps to identify specific antigens (proteins) within tissue sections utilizing an antigen-specific antibody CD21 is receptor for Epstein barr virus, but it is not necessarily positive in EBV+ tumours. CD21 is positive in follicular dendritic cell tumour, hairy cell leukaemia, mantle cell lymphoma, marginal zone lymphoma, hyaline vascular variant of castleman disease, splenic littoral cell angioma and some T-ALL.