The technique of simultaneous fluorescence immunophenotyping and interphase cytogenetics (FICTION) was applied in four cases of centroblastic-centrocytic (working formulation: follicular) lymphoma. Our aim in this study was to establish whether secondary chromosome aberrations known from a prior cytogenetic analysis were detectable in both kappa- and lambda-expressing tumor cells from the same lymphoma patient. One of the cases did indeed contain kappa- and lambda-positive tumor cells with trisomy 8. On the basis of our results, we reflect on the events that take place during early development of centroblastic-centrocytic lymphoma.