Concurrent Diagnosis of Chronic Lymphocytic Leukemia and Plasma Cell Myeloma: Report of 2 Cases and Differential Diagnostic Considerations

BACKGROUND Simultaneous occurrence of chronic lymphocytic leukemia (CLL) and plasma cell myeloma (PCM) is an uncommon hematological condition, with most patients presenting in late adult life. When these diagnoses occur concurrently, it often poses diagnostic challenges to the pathologist, with other important differential diagnoses including lymphoplasmacytic lymphoma, marginal-zone lymphoma, and chronic lymphocytic leukemia with plasmacytoid differentiation. Ancillary studies are indispensable in arriving at a reliable diagnosis in this clinical scenario. CASE REPORT We present 2 cases of simultaneous CLL and PCM that were diagnosed in our facility. The bone marrow in these patients showed increased plasma cells with a separate population of neoplastic lymphoid cells. Bone marrow examination and ancillary studies (immunohistochemistry, fluorescence in situ hybridization, and molecular studies) were performed in both cases to arrive at the diagnosis and rule out other important differential diagnoses. While the first patient was still being observed at the time of writing this report, and found to be clinically stable during his last clinic visit, the second patient succumbed to the disease as a result of gram-negative sepsis. CONCLUSIONS CLL and PCM can occasionally co-exist, posing diagnostic challenges to the pathologist. Ancillary diagnostic techniques are important in making a correct diagnosis. Making an accurate diagnosis is vital as this will guide appropriate treatment strategies. Whenever these 2 conditions occur simultaneously, patients often succumb as a result of progression of PCM.