A 2 year old Standardbred filly presented with a chief complaint of thrombocytopenia. The filly had a two week history of respiratory disease with episodes of epistaxis and melena. The filly was referred to Cornell when her platelets decreased to 7,000/uL. On presentation, the filly had petechiae on her mucous membranes and severe peripheral edema. The filly's signs were attributed to immune-mediated thrombocytopenia, and she was treated with a tapering dose of dexamethasone. The filly's platelet count improved, but she continued to have bouts of pyrexia. It was suspected that a paraneoplastic syndrome was causing the filly's signs, but even with extensive testing, the diagnosis of lymphoma or other neoplasia could not be made. When the filly was finally euthanized one month later and subsequently necropsied, the final diagnosis was alimentary B cell lymphoma.