[MRI-guided breast microbiospy or macrobiopsy: which is the best option for a small tumor?].

The choice of the optimum therapeutic strategy for breast cancer depends on the histological diagnosis of the sample obtained by biopsy. The microbiopsy is the preferred method as it provides an accurate diagnosis of the histological type as well as the main prognostic factors, whilst being simple, fast and inexepensive. However, some infraclinic breast tumors are not accessible by conventional guidance due to excessive depth inside the breast, their small size or technical inability to image them by mammography or ultrasonography. In those cases, the MRI guidance may help to perform the biopsy. Most MRI biopsies are made by large-core needle that are known to alter the histological structure of the tumor and to disturb the anatomopatholgical analysis (size and surgical margin). Those are very important elements to know before treatment. Our case report details an original technique of MRI microbiopsy of a deep 4mm opacity found on the occasion of a patient's mammography. The operative specimen revealed an invasive ductal carcinoma of 4mm diameter which scored III on the Elston and Ellis scale (oestrogen and progesterone receptors tested negative and HER-2 was over-expressed). It was associated with a high grade in situ ductal carcinoma. No systemic treatment was prescribed due to the small size of the carcinoma. The development of partially or totally amagnetic microbiopsy pistols would help perform microbiopses guided by MRI.