Chromosome 1 aneusomy, identified by interphase cytogenetics, in mammographically detected ductal carcinoma in situ of the breast.

Because of the relative rarity of ductal carcinoma in situ (DCIS) in the premammographic screening era, the unavailability of adequate fresh tissue for culture, and the lack of cytogenetic expertise in most pathology departments, there is little information on karyotypic abnormalities in DCIS. The purpose of this study was to investigate the frequency of chromosome 1 aneusomy in DCIS, using interphase cytogenetic techniques, and to correlate the findings with nuclear grade. Twenty-one cases of DCIS, identified in a mammographically screened population, were studied by in situ hybridization. Chromosome 1 numbers were identified in interphase nuclei in conventional histology sections, using a specific centromeric probe (pUC 1.77). In each case, 100 tumour nuclei were compared with 100 normal nuclei. Eighteen of 21 (86 per cent) cases were aneusomic for chromosome 2. This included 15 of 16 (94 per cent) pure comedo or predominantly comedo DCIS. Fifteen of 16 (94 per cent) DCIS with grade 3 nuclei and 3 of 5 (60 per cent) cases with grade 2 nuclei were aneusomic. One case with grade 3 nuclei (a comedo carcinoma) was negative. We conclude that chromosome 1 aneusomy precedes invasion and is a relatively consistent occurrence in those DCIS with high nuclear grade.