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Fibroadenoma (FA) is a benign breast tumour that occurs in about 25% of women. Cytogenetic studies suggest that numerical chromosomal aberrations may contribute to tumorigenesis, but chromosomal instability is still poorly characterised in breast cancer. The aim of this study was to investigate numerical alterations of chromosome 21 in 15 breast FAs. All samples were analysed by classical cytogenetics and by fluorescence in situ hybridisation (FISH) for chromosome 21 DNA sequences. Classical cytogenetics analysis showed that all cells were diploidies with modal number varying between 43 and 47 chromosomes, and clonal chromosome alterations in 46.7% of tumours. Clonal numerical alterations involved, preferentially, chromosomes 8, 10, 12, 16 and 21. FISH analysis showed a statistically significant difference for chromosome 21 monosomy between seven samples and control group. This monosomy varied from 24.5% to 43.5% of analysed cells. The presence of chromosomal alterations in FAs may be a consequence of the proliferation process and is probably not related to the aetiology of this type of lesion. The study of benign proliferations and comparison with chromosome alterations in their malignant counterparts should result in an understanding of the genes acting in cell proliferation alone and those that cause these cells to both undergo malignant transformation and become invasive.

Gastric cancer is the third most frequent type of neoplasia and the second most important cause of death in the world. ACP01 is the first gastric adenocarcinoma cell line developed in Brazil. To evaluate chromosomal aberrations implicated in gastric carcinogenesis, we analysed three different passages (6th, 12th and 35th) of ACP01 cell line by fluorescence in situ hybridisation using chromosome 8 alpha-satellite probe. Most of the chromosome 8 alterations found involved a numerical increase of this chromosome. Chromosome 8 trisomy was detected in all cases, varying from 37% (6th passage) to 67% (35th passage), and chromosome 8 tetrasomy (also observed in all passages) varied from 2.5% (6th passage) to 30% (35th passage). The presence of five signals for chromosome 8 was observed in all passages with the highest frequency found in the 12th passage (20%). Our results confirm that trisomy of chromosome 8 is a common biological phenomenon in adenocarcinoma of stomach and can be used as a gastric mucosa malignancy marker. Although gastric tumours are frequent neoplasias, papers on their cytogenetics are scarce in the literature. It is, therefore, necessary to conduct new studies aiming to identify peculiar genetic characteristics of a tumour, which might help in diagnosis and prognosis of this disease, besides allowing more accurate therapeutic conduct to be established.