SEPARATE CLONES IN CONCOMITANT MULTIPLE-MYELOMA AND A 2ND B-CELL NEOPLASM DEMONSTRATED BY MOLECULAR AND IMMUNOPHENOTYPIC ANALYSIS

The occurrence of multiple myeloma (MM) and a second B-cell neoplasm i n the same patient is a rare event. We present 2 such patients, and pr ovide evidence to support the presence of separate clones in these coe xisting neoplasms. Tn the first case, MM became evident 14 months afte r the diagnosis of chronic lymphocytic leukemia (CLL). In past reports , most occurrences of this association, when investigated, have been r egarded to be biclonal disease processes; however, with few exceptions , most were documented by immunologic studies alone. To establish the clonality in our case of CLL with MM, we examined both immunophenotypi c data obtained by standard two-color flow cytometric analysis, and pa tterns of immunoglobulin gene rearrangement, using standard Southern a nalysis and hybridization with P-32-labelled J(H) and J(K) probes. Thi s provided evidence for the presence in this patient of two separate m onoclonal populations of B cells, manifested as light chain restrictio ns and gene rearrangements which differed in blood (CLL) and bone marr ow (MM) samples. In the second case, MM presented simultaneously with bone marrow lymphocytosis and abnormal peripheral lymphocytes. Clonali ty studies on blood were not done. Bone marrow B-cell gene rearrangeme nt studies, however, revealed the presence of three bands in the J(K) blot of significantly different intensities, suggestive of two monoclo nal populations. A monoclonal population of small cells with surface B markers and surface IgM was demonstrated by flow cytometry, while a s econd population of larger cells with intracytoplasmic IgG matching th e patient's serum monoclonal protein was detected by immunofluorescenc e microscopy. The results in these 2 cases expand previous findings of the rare association of MM with a second B-cell neoplasm, and demonst rate the usefulness of molecular diagnostic investigation.