Clonal chromosome abnormalities in human breast carcinomas II. Thirty‐four cases with metastatic disease

Cytogenetic analysis was performed on a selected series of short‐term cultures from 34 patients with documented metastatic breast carcinoma. The majority of tumor cells were hyperdiploid, with clonal structural alterations observed in 94% of patients (32/34). The most common numeric changes were –2, –15, and –18. Chromosome 20 was the most frequently overrepresented (in near‐3n tumors only). Clonal structural chromosome alterations included isochromosomes, terminal deletions, and, most frequently, unbalanced non‐reciprocal translocations. Chromosomes most often involved in structural rearrangements included 1, 7, 11, and 6 (accounting for 24.7%, 10.3%, 9.1%, and 7.0% of breakpoints, respectively). When the breakpoints of clonal structural abnormalities were analyzed, they were shown to cluster to several chromosome segments, including 1p11‐q21, 7pter, 11p12‐q12, and 6q11–21. An analysis of the net gain or loss of specific chromosome segments was also performed, with the most consistent tendency observed being the over‐representation of 1q, 6p, 7, and 11. The most frequent losses included 1p, 6q, 7, and 11q. © 1993 Wiley‐Liss, Inc.