Chromosomal analysis of proliferative and malignant breast disease by chromosome in situ hybridization

Abstract

The development of chromosome in situ hybridization technique (CISH) using chromosome specific DNA probes allows assessment of numerical and structural chromosome aberrations in routinely processed paraffin-embedded sections with preservation of histological details for analysis. A previous study using fluorescent technique (FISH) has reported losses in chromosomes 16, 17, and 18 in hyperplastic and malignant breast lesions and gains of chromosome 1 in in situ and invasive breast cancer. In this study we have applied the technique of CISH in proliferative and malignant breast lesions to detect numeric chromosome aberrations and to investigate whether CISH can help distinguish between proliferative lesions and neoplastic lesions and therefore contribute to diagnosis. Paraffin blocks of normal breast, adenosis, epithelial hyperplasia, in situ and invasive ductal carcinomas from excision specimens of eight patients with invasive or in situ carcinomas were obtained. Paraffin sections 5 pm thick were digested with proteinase K. Hybridization was performed using biotin labelled DNA probes specific for chromosomes 8, 16, 17 (ATCC, USA) and X (generous gift of Dr A. H. N Hopman). The hybridization signals were detected using Avidin Biotin Complex - peroxidase technique. About 200 nuclei were evaluated for the number of signals in each preparation. The cut off point of more than 45% of the enumerated nuclei showing only one signal and more than 10% with three signals or more were taken as representing deletion or aneusomy respectively. The normal breast epithelium displayed no loss or gain of chromosomes. Gain in chromosome 17 was noted in two and chromosome 8 in all of the four adenosis lesions respectively. Gain in chromosome 8 was also noted in one case of epithelial hyperplasia. Gain of chromosomes X, 8, 16, 17 was found in comedo, solid, cribriform and micropapillary ductal carcinoma in situ in variable proportions. The two cases of invasive ductal carcinoma showed gain of chromosomes 8, 16 and 17. This study illustrates gain of similar chromosomes in both proliferative and malignant breast lesions. This supports the view that hyperplasia may be part of a sequence of progression to malignancy in breast carcinoma. Gain in chromosome 8 seems to be commonly found in breast diseases. The use of CISH as a diagnostic adjunct remains to be elucidated by study of more cases.