In situ hybridization of chromosome 6 on fine‐needle aspirates from breast carcinomas: Comparison of numerical abnormalities and ER/PgR status and staining pattern

The estrogen receptor (ER) gene is located on chromosome 6. The aim of our study was to investigate whether numerical chromosomal aberrations were reflected in estrogen/progesterone receptor (PgR) status and staining pattern. Fine-needle aspirates from 51 breast carcinomas were investigated immunocytochemically for ER/PgR and by in situ hybridization technique using digoxigeninlabeled a-satellite probe for chromosome 6. Cases with$70% two-signal nuclei were regarded as disome; the remaining tumors showed aneusomy with a variable number of signals. Aneusomy was found in 32 tumors (63%), whereas 19 (37%) had a normal number of chromosome 6. Chromosomal gain occurred in all aneusome cases except one. ER- and/or PgR-positive tumors had an equal distribution of disomy and aneusmy. Variable ER staining pattern or ER and/or PgR negativity was associated with numerical aberrations in chromosome 6 in 76% of the tumors. Cancers with uniform ER staining pattern all had normal chromosome number. Diagn. Cytopathol. 16:420‐424, 1997. r 1997 Wiley-Liss, Inc.