CD20-Negative Primary Bone Marrow Large B Cell Lymphoma: A Report of Two Cases with Review of Literature

We describe diagnostic and therapeutic challenges in this rare entity of CD20-negative B cell lymphomas. They comprise only 1 to 2% of all B cell lymphoma with four subcategories. However, with an increasing understanding of these cases, novel entities have been recognized. Workup, treatment, and follow-up of two CD20-negative B cell lymphoma cases, including a novel entity, have been described. A novel case of triple expresser CD20-negative B cell lymphoma and plasmablastic lymphoma has been diagnosed. The absence of CD20 leads to the abolishment of the targeted drug (rituximab) from the treatment regimen. These cases render the importance of extensive immunohistochemistry and fluorescence in situ hybridization workup for diagnosis of this rare entity. Treatment also remains a challenge as immunotherapy with CD20-targeted drugs cannot be given.