Additional copies of 1q in sequential samples from a phyllodes tumor of the breast

Cytogenetic and fluorescent in situ hybridization (FISH) analysis has been performed on consecutive samples, taken 4 weeks apart, from a phyllodes breast tumor. This revealed the presence of two different chromosome 1 derivatives, namely a dic(1;10) (q10;q24) in the first sample and an i(1) (q10) in the second. In one cell out of 25 from the second sample both derivative chromosomes were seen. A chromosome 21 was lost in both samples. These results are consistent with phyllodes tumors having a clonal origin.