The chromosomal findings in 10 adenoid cystic carcinomas (ACC) of the salivary glands are described. Clonal numerical deviations as the sole anomaly were detected in four cases and structurally rearranged stemlines and sidelines in four cases. An apparently identical t(6;9)(q23;p2 I) was found in two tumors; in one case the translocation was part of the abnormal stemline and in the other case it was the sole anomaly in a single variant cell. A similar or identical t(6;9)(q21-24;p 13-23) has recently been reported in three of I5 previously published cases of ACC. The three remaining tumors with abnormal stemlines all had rearrangements of chromosome 9, including t( I ;9)(q21 ;p2 I -22), der(9)i( )(q I O)inv(9)(q I2q I 3). and der(X)t(XS)(pZI ;p22-23), respectively. The latter case also had a t( 17; I8)(p I Z;q I I .2) that was common to both abnormal clones present in this tumor.
In addition to other abnormalities, the clone with der(X)t(X9) also showed a del(6)(q I3q2I). In two cases fluorescence in situ hybridization (FISH) was used for further characterization of the marker chromosomes. A survey of the present findings together with previous results from I 5 ACC clearly demonstrates *at rearrangements of 6q2 1-24 (deletions or translocations in I I cases), 9p 13-23 (translocations in seven cases), and I7pl2-I 3 (translocations in three cases) are recurrent, and often primary, in ACC, and that the t(6;9)(q21-24;~13-23), found in five tumors, is a non-random, primary aberration. Genes Chmnosorn Cancer /0:1/5-/2/ (1994).