<prompt> A 63 year old man presents with splenomgaly and lymphadenopathy. Immunophenotype was positive for CD 19, CD79b and FMC7. The most likely diagnosis is:Hairy cell leukemiaMantle cell Lymphoma MCLChronic Lymphocytic Leukemia CLLFollicular Lymphoma  <response>: Answer is B Mantle cell Lymphoma Coexpression of the B lymphocyte lineage marker CD 19 and T lymphocyte marker CD5 is unique to CLL and mantle cell Lymphoma. CLL can be differentiated from MCL be expression of CD79b and FMC-7 both of which are absent in CLL and positive in 11CL- Handbook of clinical immunology 2nd245 CU can be differentiated from MCL by expression of CD79b and FMC-7 both of which are absent in CLLSLL and bright in MCL -Handbook of human Immunology 2d245 