Expression of PAX-5 in B Cell Hodgkin and Non Hodgkin Lymphoma.

Background: B-cell malignancies including Precursor B-cell lymphoblastic lymphoma/leukemia and Hodgkin Lymphoma show a wide spectrum of B-cell differentiation from early stage B-cell precursors to mature B-cells ending in terminal differentiation to plasma cells. Pan-B-cell antigens routinely used for the diagnosis of B-cell lymphoma, include CD19, CD20, CD22 and CD79a.PAX-5 protein, also known as B-cell-specific activation protein is a B-cell-specific transcription factor; essential for commitment and functional maintenance used in the diagnosis of B cell Hodgkin and non-Hodgkin lymphoma. PAX-5 show nuclear positivity in B cell lymphomas and moderate (dim) positivity in Hodgkinlymphoma Reed Sternberg cells make this marker ideal for diagnosing B cell malignances. Objective: To determine the expression of PAX-5 in B cell Hodgkin and non-Hodgkin Lymphoma in order to improve the diagnosis of B-cell lymphomas. Methods: In this Prospective study, all the cases of B cell lymphoma diagnosed at The Aga Khan University Hospital, Karachi from July 2010 to July 2011were included. A panel of Immunohistochemical stain was performed in all cases along with additional PAX- 5 stain with appropriate controls. Results: Total 125 cases were included. Hodgkin Lymphoma (Mixed cellularity) was the commonest B-cell lymphoma subtype, 32 (25%) cases. Other common subtypes included Hodgkin lymphoma (Nodular sclerosis subtype), diffuse large B-cell lymphoma and B lymphoblastic lymphoma. Conclusion: This study demonstrates that PAX-5 is the most sensitive and reliable immuhohistochemicalmarker in the diagnosis of B cell Hodgkin and non-Hodgkin lymphoma.