Numerical abnormalities of chromosome 7 in interphase cell nuclei of breast carcinoma have no impact on immunohistochemically determined EGFR status

Aim of study: To investigate the relationship between epidermal growth factor receptor (EGFR) status and numerical aberrations of chromosome 7 in breast carcinomas. Design: In situ hybridization (ISH) of interphase cell nuclei on air-dried fine-needle aspirates (FNAC) from 33 breast carcinomas was evaluated for numerical abnormalities in chromosome 6, 7, 12 and 17. Immunohistochemical staining of EGFR was performed on corresponding histological specimens. Results: 78% of the tumours were aneuploid by ISH. Aneusomy of chromosome 7 was found in 18 cases (60%). EGFR overexpression was observed in 30% of the carcinomas, and seven of nine were aneuploid by ISH. The same percentage of chromosome 7 aneusomy was found in both EGFR-positive and -negative cases. Five of seven EGFR-positive tumours revealed aneusomy of chromosome 7. Conclusion: Numerical gain of chromosome 7 is a common finding, occurring in about 60% of breast carcinomas. Most EGFR-positive tumours are aneuploid and show numerical gain of chromosome 7, but abnormal numbers of chromosome 7 have no impact on the EGFR status.