Immunohistochemical detection of cox-2 expression in primary MM cells. Bone marrow samples from 4 patients stained for cox-2 expression. (A-C) Marrow biopsies from 3 patients with myeloma that contains mutated N-RAS or K-RAS. (D) Marrow biopsy from a patient with monoclonal gammopathy of undetermined significance (MGUS). A few plasma cells in each biopsy are depicted with black arrows. Original magnification for all panels, × 40.