A case of multiple myeloma with two subclones producing separately kappa and defective gamma chains.

A case of multiple myeloma is described that contained two morphologically identical but immunologically diverse subpopulations. One of the subclones produced only kappa chains, whereas the other contained only gamma chains. Additional immunohistologic investigations revealed production by one of the subpopulations of defective gamma chains that were devoid of demonstrable Fd parts. It could not be decided whether this was due to a structural or an antigenetical defect. Furthermore, only the kappa-producing subclone exhibited J-chains. Based upon these findings and their possible cause and on respective findings concerning other B-cell neoplasias, it is concluded that the consequent application of an ever-increasing number of different immunologic markers, in order to better classify malignant lymphomas, will eventually result in the reverse, namely, in a complete breakup of this group of malignancies into individual cases.