Figure 1.

Bone marrow biopsy findings pre- and post-treatment with daratumumab. (A) Bone marrow biopsy pre-treatment with daratumumab. Bone marrow (BM) aspirate (500x magnification), core biopsy (100x magnification) and immunohistochemical stains (100x magnification) performed on the core biopsy. The findings show decreased erythropoiesis with left shift as demonstrated by scattered E-cadherin-positive pronormoblasts and very rare hemoglobin-positive maturing erythroids, a normal number of myelomonocytic elements (positive for myeloperoxidase) and 5-9% CD138-positive plasma cells. (B) BM biopsy post-treatment with daratumumab. BM aspirate (500x magnification), core biopsy (100x magnification) and clot section (100x magnification). The findings show a normocellular BM for age, with morphologically unremarkable trilineage hematopoiesis, including an adequate number of erythroid precursors. CD138 immunohistochemical stain demonstrates increased plasma cells (up to 10%). κ and λ light chain in situ hybridization demonstrates κ light chain restriction within the plasma cells.