Splenic Diffuse Red Pulp Small B-Cell Lymphoma with Overlapping Clinical and Immunophenotypic Features with Hairy Cell Leukaemia: A Case Report and a Review of the Literature.

BACKGROUND: Splenic B-cell lymphomas and leukaemias include hairy cell leukaemia, splenic marginal zone lymphoma, splenic diffuse red pulp small B-cell lymphoma, and splenic B-cell lymphoma/leukaemia with prominent nucleoli. The main diagnostic challenge is to differentiate between splenic B-cell lymphomas and leukaemias due to highly overlapping clinical, morphologic, and phenotypic features in the absence of splenectomies for diagnostic purposes.

CASE PRESENTATION: We describe a case of a 78-year-old woman who presented with weight loss and was subsequently found to have pancytopenia, lymphocytosis, and splenomegaly. Peripheral blood smear showed a homogenous population of small- to medium-sized lymphocytes having oval nuclei, condensed chromatin, and villous cytoplasmic projections. Bone marrow showed B-cell infiltrate in a predominantly intrasinusoidal pattern. Except for cyclin D1 and BRAF, the immunophenotype was similar to that of hairy cell leukaemia. This was further supported by the lack of BRAF p.V600E mutation by polymerase chain reaction. A diagnosis of splenic diffuse red pulp small B-cell lymphoma was thus favored based on the lack of cyclin D1 expression and pattern of infiltration in the bone marrow biopsy.

CONCLUSIONS: Awareness of this infrequent clinical presentation and immunophenotype of splenic diffuse red pulp small B-cell lymphoma is crucial for diagnosis and devising appropriate therapeutic strategies for the patient.