Nuclear focus formation in response to chemotherapy. Tumor specimens were obtained by core needle biopsy before and 18 to 24 hours after the first cycle of epirubicin plus cyclophosphamide (EC) treatment. Immunohistochemical findings from representative cases for γH2AX, conjugated ubiquitin (Ub), BRCA1, and Rad51 are shown. Graphs at right demonstrate changes in nuclear foci score after EC treatment in all cases analyzed. The red, blue, and black lines indicate cases with increased, decreased, and unchanged scores, respectively. The thickness of the lines proportionally reflects the number of cases. The thinnest line (γH2AX score 3 to 3) and the thickest line (Ub, score 0 to 0) represent 1 and 34 cases, respectively. n, number of cases analyzed.