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 t he premammographic screening era, the unavailability of adequate fresh tissue for culture, and the lack of cytogenetic expertise in most pat hology departments, there is little information on karyotypic abnormal ities in DCIS. The purpose of this study was to investigate the freque ncy of chromosome 1 aneusomy in DCIS, using interphase cytogenetic tec hniques, and to correlate the findings with nuclear grade. Twenty-one cases of DCIS, identified in a mammographically screened population, w ere studied by in situ hybridization. Chromosome 1 numbers were identi fied 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) ca ses were aneusomic for chromosome 2. This included 15 of 16 (94 per ce nt) pure comedo or predominantly comedo DCIS. Fifteen of 16 (94 per ce nt) 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 carci noma) was negative. We conclude that chromosome 1 aneusomy precedes in vasion and is a relatively consistent occurrence in those DCIS with hi gh nuclear grade.