Small lymphocyte–like plasma cell myeloma morphologic features. A, Bone marrow aspirate. The plasma cells are small with a scant rim of cytoplasm with an appearance similar to that of a mature lymphocyte (Wright, ×1,500). B, Bone marrow core biopsy specimen. Small lymphocyte–like plasma cells infiltrate the marrow in an interstitial and nodular pattern (H&E, ×300). C, Appearance of nodular focus at higher power. Small lymphocyte–like plasma cells demonstrate mature condensed chromatin and minimal cytoplasm (H&E, ×600). D, CD138 immunohistochemical staining (B-A38, Serotec, Oxford, England, 1:20 dilution, Benchmark automatic stainer with standard antigen retrieval). Diffuse CD138 immunohistochemical labeling of small lymphocyte–like plasma cells is present (×600).