(A) Bone marrow aspirate with few plasma cells (original magnification ×100, Giemsa stain). (B) Flow cytometry plot of bone marrow showing λ-positive plasma cells (in red) and polyclonal B cells (in green). Anti-κ (TB 28-2) allophycocyanin stain (APC), Becton, Dickinson (BD), catalogue number: 341108; Anti-Λ (1-155-2) APC-H7, BD, catalogue number: 656648. (C) Heavy chain in blue; Λ light chains in red. (D) Amyloid deposits in a fat aspirate (original magnification ×10, congo red staining, polarized light). Professional illustration by Patrick Lane, ScEYEnce Studios.