In situ hybridization for light chains in a case of myeloma. Marrow. In situ hybridization for either kappa or lambda immunoglobulin light chain RNA was performed using biotin-labeled oligonucleotide probes, followed by a streptavidin-alkaline phosphatase detections system and colored substrate formation. In the left panel, the color reaction in the cytoplasm confirms that plasma cells express monoclonal kappa light chain as reflected in the intense cytoplasmic dark blue to black staining. In the right panel there is no reactivity of plasma cells with the lambda specific probe (absence of cytoplasmic staining). In a case in which plasma cells are synthesizing lambda light chains, the lambda reaction would be positive (cytoplasm dark blue to black) and the kappa reaction negative. This result is indicative of a clone of neoplastic plasma cells synthesizing a monoclonal kappa light chain.
In situ hybridization for Epstein-Barr virus early RNA (EBER) in a case of plasmablastic lymphoma from an HIV-positive patient. Note the nuclear brown stain, reflecting the presence of EBER in the lymphoma cells.