Peripheral blood smear, bone marrow aspiration and biopsy, and immunohistochemical staining results of the patient. The peripheral blood smear (A) revealed the presence of medium-sized to large neoplastic lymphoid cells (indicated with red arrows, Wright stain, ×400). The bone marrow aspiration (B, C) and touch print (D) showed normocellular marrow with increased infiltration of large neoplastic lymphoid cells (indicated with red arrows, Wright stain, ×400) and plasma cells. The bone marrow biopsy (E, F) showed normocellular marrow with diffuse infiltration of large neoplastic lymphoid cells (Hematoxylin & Eosin stain, ×400). Subsequently performed immunohistochemical staining showed the presence of large neoplastic lymphoid cells with strong membranous positivity for CD20 (G) and negativity for both CD3 and CD10 (H, I), but nuclear positivity for both BCL-6 and MUM1 (J, K). In addition, increased plasma cells showed positivity for CD138 (L).

Abbreviations: CD, cluster of differentiation; BCL-6, B-cell lymphoma 6; MUM1, multiple myeloma oncogene 1.