The thesis focuses on identifying molecular genetic changes relevant for the development of breast cancer. TP53 is the most frequently mutated gene in human cancer, and this gene has a central role also in breast cancer. Both congenital variants and somatic TP53 mutations in the tumour tissue was studied. The mutational status of TP53 was shown to be a strong prognostic marker for breast cancer, and various types of mutations had different effects on the outcome of the disease.
The microarray technology, which allows the simultaneous analysis of thousand of genes, was used to uncover the different gene expression profiles of the two main histological types of breast cancer. The sub-classification of breast tumours based on gene expression profiles were further explored, and shown to be a powerful prognostic marker of breast cancer.