Peripheral blood smear with a hairy cell with an oblong nucleus and threadlike/hairlike cytoplasmic extensions. Case description A 56 year old Caucasian female presented with fatigue, easy bruisability and gingival bleeding of 3 months duration. Physical exam showed a palpable spleen tip. A complete blood count revealed pancytopenia. Peripheral blood smear showed the presence of lymphocytes with oblong nuclei with threadlike cytoplasmic extensions (hairy cells). Flow cytometry was positive for CD 103 and CD 11c, distinct markers for hairy cell leukemia. Bone marrow biopsy showed marrow infiltration with lymphoid cells, 70% being hairy cells enmeshed in an extra-cellular matrix of reticulin fibrils giving them the classically described fried egg appearance. Based on these findings, the patient was diagnosed with Hairy Cell Leukemia and treated with a five day infusion of Cladribine. Hairy Cell Leukemia is a rare and indolent lymphoproliferative malignancy which commonly presents with s