CD 7 or the Cluster of differentiation 7 test is performed on blood sample to measure the level of CD-7 to confirm T cell lymphoma and also during the treatment and after the treatment of T cell Lymphoma. It is also found on natural killer cells, and a small sub-population of both normal and malignant B-cells. It is also known as immunohistochemistry (IHC). Immunohistochemistry combines histological, immunological and biochemical techniques for the identification of specific tissue components by means of a specific antigen/antibody reaction tagged with visible label. It is widely used for diagnosis of cancers because specific tumor antigens are up regulated in certain cancers.