<prompt> TRAP positivity is seen with:CMLHairy cell leukemiaCLLFollicular lymphoma  <response>: B i.e. Hairy cell leukemiaRef: Robbins Pathology, 9th edition, page 603Explanation:Hairy Cell Leukemia:Rare chronic leukemia that commonly presents with massive splenomegaly, with tumor cells containing hair-like projectionsAlso known as leukemic reticuloendotheliosis.Clinical:Commonly presents with massive splenomegaly with obliteration of white pulp and involvement of red pulp, pancytopenia 50, marrow fibrosis, monocytopenia, infections in 13.Bone marrow aspiration biopsies unsuccessful dry tap in 30 - 50 due to marrow fibrosis.Peripheral Smear:Tumor cells are larger than small lymphocytes, modest pale blue a granular cytoplasm with circumferential threadlike extensions seen with phase contrast microscope, round or indentedfolded oval nuclei, no distinct nucleoli.Bone Marrow:Prominent cell borders fried egg appearance with formalin fixation.Stains:TRAP.B cell markers.CD 11c, CD25, CD103.Annexin A1. 