Clonal karyotypic abnormalities associated with reactive lymphoid hyperplasia

Cytogenetic abnormalities are important in the diagnosis and prognosis of hematolymphoid neoplasms. Although many recurrent karyotypic abnormalities are well-defined and known to underlie pathophysiologic processes contributing to malignancy, the significance of other cytogenetic changes is less clear. This uncertainty reflects an incomplete understanding of the frequency with which karyotypic abnormalities arise in benign processes. Numerous case reports and a small number of retrospective series have noted clonal cytogenetic changes in association with reactive-appearing lymph nodes. However, the incidence of such abnormalities has varied widely in published series. Here, we report the largest retrospective series of karyotypic abnormalities in association with reactive lymphoid hyperplasia published to date. Clonal karyotypic abnormalities were present in 6.3% of reactive lymph nodes with informative karyotypes and 5.1% of all reactive lymphoid tissues. These data suggest that karyotypic abnormalities are less frequently found in association with reactive lymphoid tissue than previously reported and provide a clearer picture of the baseline incidence of cytogenetic changes in benign lymphoid processes.