Annexin A1 expression in a splenic diffuse red pulp small B-cell lymphoma: Report of the first case

摘要

Sir: Annexin A1 was the first characterized member of the annexin family of proteins, and is encoded by the ANXA1 gene. It is known to be involved in a broad range of cellular processes, including inflammatory signalling, apoptosis, and differentiation. It is particularly highly expressed in cells of the haematopoietic lineage, including neutrophils, monocyte-mac-rophages, and mast cells. In the context of B-cell lymphomas, gene expression profiling has shown annexin A1 to be up-regulated in hairy cell leukaemia (HCL), and expression of the protein is considered to be a sensitive and specific marker of this entity. HCL is one of the group of splenic B-cell lymphomas that primarily involve the red pulp, along with hairy cell leukaemia variant (HCL-v) and splenic diffuse red pulp small B-cell lymphoma (SDRPL). These last two entities are placed in the new provisional category 'splenic lymphoma/leukaemia unclassifi-able'. However, there are overlapping features between some of these entities with regard to blood cytology, spleen histology, and immunophenotype. Thus, annexin A1 staining is now widely used as a specific discriminator between HCL and the other lymphomas primarily arising in the splenic red pulp. We describe a case of SDRPL with unexpected annexin Al expression in a 75-year-old female patient who presented with abdominal discomfort predominantly on the left upper quadrant of the abdomen. Physical examination revealed massive splenomegaly and no lymphadenopathy. She had a white blood cell count of 20 x 109/l. Morphological analysis of peripheral blood smears identified circulating medium-sized lymphocytes with round-shaped nuclei and thin cytoplasmic projections, which strongly expressed CD20 and CD 79 a but lacked expression of CD25, CD103, and CD123.