Hairy cell leukemia*An uncommon chronic lymphoproliferative disorder of B lymphocytes *Clinical presentation: Massive splenomegaly, hepatomegaly, and lymphadenopathy*Peripheral blood: Bicytopenia/Pancytopenia, absolute monocytopenia, absolute neutropenia, anemia, and thrombocytopenia. *Cytopenia could be due to hypersplenism, hairy cell infiltration of marrow and TNF-a secreted by hairy cells.*Hairy cells are mononuclear cells with eccentric or central round, ovoid, reniform, or convoluted nuclei. Nuclear forms tend to have a reticular chromatin pattern. Hairy cells have variable amounts of cytoplasm that is blue-gray in appearance, exhibiting thin cytoplasmic projections*Bone marrow aspirate shows "dry tap" due to marrow fibrosis*Bone marrow biopsy shows hairy cells with "fried egg appearance"*Cytochemical stain: Positive for tarate-resistant acid phosphatase *Immunohistochemical stain: Positive for Annexin A1(specific for HCL), CD20, TRAP, DBA44, T-bet*And CD103 (Frozen section)*Flowcytometry : CD11c, CD22, CD25 and CD 103. Also positive for pan-B markers like CD19, CD20, and CD22. Newly identified CD200 marker shows expression only in hairy cell leukemia and chronic lymphocytic leukemia. Treatment of choice: CladribineParametersHCLHCL-VariantSplenic Lymphoma with Villous LymphocytesBloodMorphologyNuclear shapeOvoid, reniformRoundRoundChromatinReticular +- nucleolusCoarse with central nucleolusCoarse +- nucleolusCytoplasmBlue-gray, abundantBlue-gray, abundantBasophilic, scant to moderateMonocytopenia+--TRAP stain++++-+-Aspirated marrow*-++Splenic involvementRed pulpRed pulpWhite pulpFlow cytometry CD22+++++++ CD11c++++++ CD25++-+- CD103+++--Ref: Williams Hematology 8/e chapter 95