Unclassifiable splenic B-cell lymphoma/leukemia: histologic, morphologic, immunohistochemical and genetic features. (A) Hematoxylin and eosin demonstrates a diffuse splenic infiltrate of small mature lymphocytes, atrophic/absent white pulp, and occasional blood lakes. The infiltrate is composed of mature lymphocytes (inset). (B) CD20 expression in the neoplastic lymphocytes. (C) Absence of Annexin 1 (main panel) and positive p-ERK (inset) in the neoplastic B cells. (D) Subset DBA.44 expression in neoplastic B cells. (E) Pyrogram demonstrating the BRAF c.1799T>A mutation (shaded area; percentage indicates relative abundance). Nucleotide dispensation order is indicated along the x-axis. (F-G) Peripheral blood smear demonstrating atypical lymphocytes with abundant cytoplasm, absent villous cytoplasmic extensions, and inconspicuous nucleoli.