RESUMEN
BACKGROUND: Cancer development results from the progressive accumulation of genomic abnormalities that culminate in the neoplastic phenotype. Cytogenetic alterations, mutations and rearrangements may be considered as molecular legacy which trace the clonal history of the disease. Concomitant tumors are reported and they may derive from a common or divergent founder clone. B-cell chronic lymphocytic leukemia (B-CLL) and plasma cell myeloma (PCM) are both mature B-cell neoplasms, and their concomitancy, albeit rare, is documented. CASE PRESENTATION: Here, we described a patient with prior B-CLL with secondary development of PCM. Cytogenetic and multi parametric flow cytometry analyses were performed. The B-CLL population presented chromosome 12 trisomy, unlikely the arisen PCM population. CONCLUSION: The close follow up of B-CLL patients is important for early intervention in case of development of other malignancy, such as myeloma. Our observation suggests these two diseases may have arisen from different clones. We understand that the investigation of clonal origin may provide important information regarding therapeutic decisions, and should be considered in concomitant neoplasm.