Chromosome rearrangements involving chromosome I, band p36, are among the most common aberrations in non-Hodgkin lymphomas (NHL). We have studied nine cases of NHL with add( l)(p36) using fluorescence in situ hybridization (FISH) from a series of 205 cases. Five were follicular low-grade NHL and four were follicular or diffuse high-grade NHL. Three of the five cases with follicular low-grade NHL did not contain the 14;18 translocation. The extra material on the add(l)(p36) in these three cases was derived from chromosome segment 2q3 I -qter; in one it was observed as a sole clonal rearrangement. In the two remaining cases, with t( 14;18), the add( l)(p36) consisted of material from chromosome arms 3q and 17q, respectively. In the four cases of high-grade NHL, the material added on to I p36 was derived from chromosomes 6,9, 17, and 19, respectively.
Using a I p36-specific probe, D I S94, we showed a deletion on the add( I) in one of the cases with low-grade NHL, whereas no loss was observed in one of the cases with high-grade NHL. Our study indicates that cytogenetically similar add( l)(p36) are found in both high-and low-grade NHL, and the breakpoint on I p36 as well as the origin of translocated material may vary.