Diagnostic difficulties of pure intrasinusoidal bone marrow infiltration of non-Hodgkin's lymphoma: a report of eight cases from India.

Bone marrow involvement in non-Hodgkin's lymphoma is prognostically important for appropriate management. Intrasinusoidal pattern of bone marrow infiltration is poorly identified on trephine biopsies. We analyzed the clinical, hematological and histopathological spectrum of eight cases of non-Hodgkin's lymphoma showing pure intrasinusoidal bone marrow infiltration. Fever, cytopenias and blasts in circulation were the indications for bone marrow aspiration and trephine biopsies. Flow cytometry on bone marrow and immunohistochemistry on trephine sections were done. There were five cases of T-cell hepatosplenic non-Hodgkin's lymphoma (three γδ T-cell lymphoma) and three B-cell non-Hodgkin's lymphoma (two intravascular large B-cell lymphoma and one splenic marginal zone lymphoma). Except the cases with intravascular large B-cell lymphoma, all showed variable splenomegaly without lymphadenopathy. Immunohistochemistry highlighted intrasinusoidal infiltration, which was difficult to discern on hematoxylin and eosin. This brief analysis highlights that pure intrasinusoidal infiltration of extranodal non-Hodgkin's lymphoma requires a high degree of diagnostic suspicion and can be seen in various lymphomas.