Biphenotypic plasma cell myeloma: two cases of plasma cell neoplasm with a coexpression of kappa and lambda light chains.
Plasma cell neoplasm (PCM) is a medullary and extra medullary proliferation of clonal plasma cells that occurs due to accidental translocation of proto-oncogenes into immunoglobulin (Ig) gene loci. While the majority of plasma cell neoplasms are monoclonal, up to 2% of the PCMs [1] considered being biclonal based on electrophoretic analysis, characterized by secretion of paraprotein with two distinct heavy chains or light chains are possible and present unique diagnostic challenges.


METHODS
Traditionally protein electrophoresis has been used to diagnose, characterize, and monitor progression of plasma cell neoplasm. To characterize neoplastic plasma cells, in our institution, other ancillary studies, including in situ hybridization, flow cytometric analyses of plasma cell surface markers and cytoplasmic immunoglobulins with DNA ploidy, are also utilized routinely.


RESULTS
We present two cases of plasma cell myeloma in which the neoplastic plasma cells shows production of cytoplasmic kappa and lambda light chain, with secretion of free lambda light chain only. Co-expression of kappa and lambda light chain by the same neoplastic plasma cells is a rare but reported phenomenon.


CONCLUSIONS
Our study indicates that serum electrophoresis alone could mischaracterize biphenotypic myeloma as monotypic plasma cell myelomas in the absence of additional testing methods.
Department of Pathology, University of Arkansas for Medical Sciences Little Rock 72205, AR, America.
Shahanawaz
S
Jiwani
Department of Pathology, University of Arkansas for Medical Sciences Little Rock 72205, AR, America.
Joshua
J
Bornhost
Department of Pathology, University of Arkansas for Medical Sciences Little Rock 72205, AR, America.
Daisy
D
Alapat
D000971:Antineoplastic Combined Chemotherapy Protocols / Q000627:therapeutic use; D014408:Biomarkers, Tumor / Q000032:analysis* / Q000097:blood / Q000235:genetics; D019075:Electrophoresis, Capillary; D017809:Fatal Outcome; D005260:Female; D005434:Flow Cytometry; D006801:Humans; D007145:Immunoglobulin kappa-Chains / Q000032:analysis* / Q000097:blood / Q000235:genetics; D007146:Immunoglobulin lambda-Chains / Q000032:analysis* / Q000097:blood / Q000235:genetics; D007150:Immunohistochemistry; D016130:Immunophenotyping / Q000379:methods; D017403:In Situ Hybridization; D008297:Male; D008875:Middle Aged; D009101:Multiple Myeloma / Q000097:blood / Q000175:diagnosis / Q000188:drug therapy / Q000235:genetics / Q000276:immunology*; D010641:Phenotype; D011237:Predictive Value of Tests; D012333:RNA, Messenger / Q000235:genetics; D016896:Treatment Outcome
D014408:Biomarkers, Tumor; D007145:Immunoglobulin kappa-Chains; D007146:Immunoglobulin lambda-Chains; D012333:RNA, Messenger
Biphenotypic plasma cell myeloma; light chain coexpression