Expression of CD200 in CD5 positive B-CELL lymphoproliferative disorder (B-CLL and MCL) and its role in the discrimination between these disorders

Chronic B-cell lymphoproliferative disorders (B-CLPD) are a group of clonal diseases characterized by proliferations of mature B lymphocytes in the bone marrow (BM), peripheral blood, and lymphoid tissues. Mature B-cell lymphoproliferative disorders is divided by CD5 expression into two groups: 1. CD5 (positive) diseases including B cell chronic lymphocytic leukemia (B-CLL) and mantle cell lymphoma (MCL). 2. CD5 (negative) diseases and including all the other forms of B-CLPD. Chronic lymphocytic leukemia (B-CLL) and mantle cell lymphoma (MCL) have many features in common and their differential diagnosis may be arduous, particularly when a leukemic phaseof lymphoma is the only presentation. immunophenotypic panels are often useful, with CD23 being the most validin B-CLL and in MCL suspected cases should be confirmed by immunohistochemically cyclin D1 detection but sometimeindefinite or some time negative repercussion may occur and other immunological markers and advanced cytogenetics or molecular techniques are bona fide but they add extra cost and not widely available. So we study the expression of CD 200 which is a membrane gpof the immunoglobulin superfamily in CD 5 positive mature B-cell lymphoproliferative disorders to help in differentiation. Aim of the study: - 1. To detectthe immunohistochemically expression of CD200 in CD5 +ve Mature B-cell lymphoproliferative disorders. 2. Evaluation of the value of CD200 in diagnosis and differentiating between B cell chronic lymphocytic leukemia (B-CLL) and mantle cell lymphoma (MCL). Patients, materials and methods: - This cross sectional study included 49 adult patientsand newly diagnosed by morphology and flowcytometric immunophenotyping as B-CLL for score 4-5 and MCL with score <4conducted from February 2015 to September 2016 from many centers, Baghdad teaching hospitals and private clinic. From each patient, left over samples were used. Bone marrow trephine biopsy sections were stained with hematoxylin and eosin for histopathological assessmentfurther detection for the expression of cyclin D1 and CD200were performed by immunohistochemistry technique. Results: - The patients were 36 males and 13 females newly diagnosed as CD5 positive mature B-cell lymphoproliferative disorder, 39 patients were presented with B-chronic lymphocytic leukemia and 10 were mantle cell lymphomadiagnosed by morphological assessment and flowcytometric immunophenotyping as B-CLL with score 4-5 and MCL with score <4, MCL diagnosis proved by immunohistochemically expression of cyclin D1. The result showed thatCD200 was expressed in 37 (94.9%) out of 39 chronic lymphocytic leukemia patientswhile mantle cell lymphoma cases were all negative for CD200 expression. Highly significant association between CD200 expression and B-CLL, p valuewas <0.001 and negative in 2 cases (5.1%) shown to have an advanced disease. Conclusions: - CD200 is highly expressed in B-CLL and it has a discriminative role in mature CD5 positive B-cell lymphoproliferative disorders (B-CLL and MCL). The only CD 200 negative CLL cases might related to the advanced stage of disease.