RATIONALE: Studying samples of tumor tissue from patients with cancer in the laboratory may
help doctors learn more about changes that occur in DNA and identify biomarkers related to
cancer. It may also help doctors understand how well patients respond to treatment.
PURPOSE: This laboratory study is examining tumor tissue samples from patients with breast
cancer treated with bevacizumab on clinical trial ECOG-2100 to learn more about DNA changes
and response in these patients.