κ and λ light chain immunostaining of monotypic λ PCs in a polytypic background. (A) Lymphoid aggregate (arrow) rimmed by PCs that are monotypic for λ immunoglobulin light chain. (B) PCs are negative for κ immunoglobulin light chains around the lymphoid aggregate (arrow). (C) The same case as panels A and B showing background PCs that are polytypic for immunoglobulin lights chains, λ, and (D) κ. Photomicrographic images were obtained with an Olympus BX51 microscope equipped with an Olympus DP71 camera and software. Final image preparation was performed with Adobe Photoshop CS2 for panels A and B. Original magnification 10×/0.30 UPlanFL N lens for all panels.