Correlation of levels and patterns of genomic instability with histological grading of invasive breast tumors

Pathological grade is a useful prognostic factor for stratifying breast cancer patients into favorable (well-differentiated tumors) and less favorable (poorly-differentiated tumors) outcome groups. The current system of tumor grading, however, is subjective and a large proportion of tumors are characterized as intermediate-grade tumors, making determination of optimal treatments difficult. To determine whether molecular profiles can discriminate breast disease by grade, patterns and levels of allelic imbalance (AI) at 26 chromosomal regions frequently altered in breast disease were examined in 185 laser microdissected specimens representing well-differentiated (grade 1; n = 55), moderately-differentiated (grade 2; n = 71), and poorly-differentiated (grade 3; n = 59) stage I–IV breast tumors. Overall levels of AI were significantly higher in grade 3 compared to grade 1 tumors ( P