Kappa recognizes surface immunoglobulin on normal and neoplastic B cells. In paraffin-embedded tissue, kappa shows strong staining of kappa-positive plasma cells and cells that have absorbed exogenous immunoglobulin. In the study of B-cell neoplasms, the determination of light chain ratios remains the focus. This is sound reasoning, as most B-cell lymphomas express either the kappa light chain antibody or the lambda light chain antibody, whereas reactive proliferations show a mixture of kappa- and lambda-positive cells. If only a single light chain type is detected, a lymphoproliferative disease is very likely. Monoclonality is determined by a kappa to lambda ratio of greater than or equal to 3:1, a lambda to kappa ratio of greater than or equal to 2:1, or a monoclonal population of 75% or more of the total population.