Cytogenetic abnormalities in reactive lymphoid hyperplasia: byproducts of the germinal centre reaction or indicators of lymphoma?

Non-random karyotypic abnormalities associated with non-Hodgkin lymphomas (NHLs) have been described in cases of reactive lymphoid hyperplasia (RLH). However, the frequency and types of cytogenetic aberrations detected and their clinical relevance are unknown. To address these questions, we undertook a retrospective analysis of a large series of RLH diagnosed at our institute over 8 years. Cytogenetic abnormalities were identified in 20 of 116 (17%) cases with informative karyotypes, comprising 14 (70%) structural and 11 (55%) numerical changes. Clonal (n  =  14, 70%) and non-clonal (n  =  6, 30%) abnormalities were observed. Aberrations of chromosome 14 were the most frequent (n = 8, 42%, 7 represented IgH translocations), followed by chromosome 3 (n  =  4, 3 represented BCL6 translocations), and chromosome 12 (n = 4). Abnormal karyotypes were most often associated with florid follicular hyperplasia. Isolated lymphoid organ (lymph node, tonsil or spleen) enlargement (12/20, 60%) was more common, no specific etiology was identified in 10/20 (50%) cases and only 1 of 18 patients with clinical follow-up (range 2-107 months, median 60 months) developed lymphoma. In our experience, cytogenetic abnormalities involving loci associated with B-cell NHL are not infrequently detected in RLH. Their occurrence portends low risk for lymphomagenesis, however longer follow-up is prudent to further evaluate the natural history of such cases.