ABSTRACT
Kappa and lam bda IH C for the dem onstration o f c lonality : W hen PCs or lymphoplasmacytic cells are present, K and λ IH C stains can be used to demonstrate clonality. The normal Κ:λ is 2:1. Kappa light chain monotypism is usually defined as a Κ:λ ratio of > 10:1, and λ monotypism as < 1:2. In practice, the predominance of one or the other in neoplasia is usually marked. Interpretation of cell surface staining for K and λ is difficult and should not be attempted. Occasionally, one gets lucky and sees cytoplasmic light chain restriction in a ML that does not have plasmacytoid morphologic features, but this is uncommon and K and λ IH C stains should not be done routinely in such cases.
