Aberrant Acquisition of T-cell Associated Markers in Plasma Cell Neoplasms: An Aggressive Disease with Extramedullary Involvement and Very Short Survival.

BACKGROUND: Plasma cell neoplasms can show aberrant expression of different lineage-related antigens; however, co-expression of T-cell-associated markers on malignant plasma cells is extremely rare. MATERIAL AND METHODS: This report describes clinicopathologic characteristics of three myeloma patients with emergent plasmablastic morphology and aberrant acquisition of T-cell-associated markers diagnosed in our center. An extensive literature search for similar cases was conducted, and the relevant pathologic, clinical, and prognostic characteristics were summarized. RESULTS: A total of 22 cases of plasma cell neoplasm (including the three cases reported here) showed aberrant co-expression of T-cell markers. We found an evident association between aberrant expression of T-cell markers on malignant plasma cells and extramedullary involvement, aggressive morphologic features, high proliferative index ki67 >90%, aggressive clinical course, an adverse outcome, and short survival. DISCUSSION & CONCLUSION: Due to the rarity of this aberrant phenotype and scarcity of the published data, the precise causative mechanism and its clinical implications have not yet been elucidated.