Immunocytochemistry of bone marrow myeloma cells and controls.

(A) RANKL immunostaining shows strong positivity in myeloma cells obtained by bone marrow aspirate from a patient with multiple myeloma and osteolytic lesions. (B) Negative control staining using an irrelevant antibody (pancytokeratin). (C) SaOs-2 cells, a human osteosarcoma cell line, which is known to express RANKL, served as a positive control.