Antigenic transformation in plasma cell dyscrasia

The WHO immunophenotype for plasma cell myeloma is deletion of CD19 and CD20, usual expression of CD38, CD138, and CD56, and occasional expression of CD10. Of the 39 cases of plasma cell dyscrasia in our study, the mean fluorescence intensities (MFI) of CD38, CD138, CD56, and CD19 were quantified in 30 cases. CD19 was absent in 38 of the cases (97.4%), whereas CD138 and CD38 were expressed in all 39 cases (100%). Most cases expressed CD38 and CD138 brightly with MFI values greater than 501, whereas all other marker expression was moderate with MFI greater than 301. Whereas CD38/CD56 dual expression was observed in 25 cases (64.1%), 14 failed to express CD56 (35.9%). CD56 expression was bright in 16 cases (53.3%), moderate in 2 cases (6.7%), and negative in the remaining 12 cases (40%) with MFI values of 200 or less. CD117 expression was positive in 9 of 24 cases (37.5%). In 32 of 39 cases, 27 were negative for CD20 (84.4%) and 28 were negative for CD10 (87.5%). Our results point to the value of quantitative fluorescence intensity in the flow cytometric evaluation of CD molecular expression or deletion in the diagnosis of hematopathologic disorders, such as plasma cell dyscrasia.