The gene expression profile detected in the core needle biopsy of a breast tumour is representative of gene expression in the whole tumour. A study published today in the open access journal Breast Cancer Research confirms the reliability of core needle biopsy as a tool in breast cancer diagnosis and prognosis. The study also shows that the gene expression profile of a core needle biopsy might be more accurate than the profile of a surgical sample taken from the same tumour, after the biopsy was carried out. According to the study results, the biopsy procedure seems to trigger the expression of genes involved in wound healing as well as tumour invasion and metastasis, thus modifying the gene expression profile of subsequent surgical samples.