Myeloma cells express the following antigens, except:
ExplanationD. Non-neoplastic polyclonal plasma cells are normal components of a bone marrow aspirate and increase in many benign inflammatory conditions, need to be distinguished from neoplastic, clonal plasma cells of plasma cell dyscrasias. Like normal plasma cells, myeloma cells also express CD79a, CD138 and CD38. However, in contrast to normal plasma cells, myeloma cells infrequently express CD19. Identification of the plasma cells has typically been based on the demonstration of high CD38 and CD138 expression. In addition to CD38 and CD138, normal plasma cells are generally positive for CD19 and CD45 whereas abnormal plasma cells characteristically lack CD19 and variably express CD45. Further the clonality of plasma cells can be confirmed based on the light chain restriction pattern, i.e. presence of either kappa or lambda cytoplasmic immunoglobulin light chains. Expression of CD56 (Neural cell adhesion molecule) is also commonly used to identify abnormal plasma cells, since normal plasma cells typically lack CD56. Waldenstrom’s macroglobulinemia is typically associated with lymphoplasmacytoid cells which are typically CD19 and CD38 positive and variably express CD138. In contrast to typical plasma cell neoplasms, however, the plasma cells in lymphoplasmacytic lymphoma are almost always CD19 and CD45 positive. CD20 is not expressed by normal plasma cells. The most important findings that characterize malignant versus normal plasma cells are: absent or low expression of CD27, CD19 and/or CD45, and increased expression of CD28, CD33, CD117 and/or CD56, and monoclonal light chain restriction.
