WHOLE-ARM T(1 16) AND I(IQ) AS SOLE ANOMALIES IDENTIFY GAIN OF IQ AS A PRIMARY CHROMOSOMAL ABNORMALITY IN BREAST-CANCER

Cytogenetic analysis of four ductal breast carcinomas revealed net gain of 1 q in all tumors. In the first tumor, the only change was that one chromosome 16 was replaced by a derivative chromosome consisting of 16p and 1 q. The same unbalanced whole-arm translocation was also found in the second tumor, as the only aberration in one of four abnormal clones. In the last two cases, which also were characterized by cytogenetically unrelated clones, an extra i(1 q) was present in one clone in both tumors as the sole aberration. Our findings suggest that gain of 1 q is a primary chromosomal abnormality in breast carcinomas, in the sense that it is an early event that precedes the acquisition of more complex changes.