Chromosome aberrations in desmoid tumors. Trisomy 8 may be a predictor of recurrence.

Cytogenetic analyses of short-term cultures revealed clonal chromosome aberrations in 6 of 13 desmoid tumors. These aberrations included two consistent events, trisomy 8 (n = 4) and trisomy 20 (n = 3), which have not been reported previously in desmoid tumors. Because trisomy 8 was found in two recurrent desmoid tumors, we used fluorescent in situ hybridization (FISH) methodology to evaluate chromosome 8 in 25 paraffin-embedded and frozen desmoid specimens. The FISH studies demonstrated that both patients with cytogenetic trisomy 8 at the time of recurrence also had had trisomy 8 in primary tumors 4 years earlier. The proportion of trisomy 8 cells in these cases did not change substantially between original diagnosis and recurrence. The FISH studies also revealed trisomy 8 in one recurrent desmoid tumor which had been cytogenetically unremarkable and revealed trisomy 8 in one recurrent desmoid that had not been karyotyped. Four of six patients with trisomy 8 had been followed for more than 1 year, and the desmoid tumors in each of these 4 patients recurred. By contrast, recurrence was noted in only 2 of 17 patients whose desmoid tumors lacked trisomy 8. Our findings demonstrate that trisomy 8 and trisomy 20 are nonrandom aberrations in desmoid tumors. Trisomy 8 appears to be associated with an increased risk of recurrence.