[MR-guided stereotactic breast biopsy: technical aspects and preliminary results]

To assess the feasibility and accuracy of cytologic and microhistologic breast biopsy using a MR imaging-guided stereotactic system with MR-compatible non-magnetic needles.

Between December 2001 and September 2002, cytologic and microhistologic sampling of 14 lesions (12 patients) was performed in our radiology department using a commercially available MR-guided stereotactic device. MR-compatible non-magnetic needles or mixed kit (non-magnetic coaxial needle + conventional ferromagnetic needle) were used. Of the 12 patients examined, 2 were undergoing MR examination because of genetic/familial risk, 4 during post-operative follow-up and the remaining 6 for contradictory mammographic and sonographic findings. Ten of the 14 lesions were visible on MR alone. The mean lesion diameter was 12 mm (range 5-30 mm).

The procedure was relatively simple and feasible. The procedure took 45 minutes on average. The cytologic samples were adequate in 4/14 cases (29%). The diagnosis was absence of malignant cells in one case, ductal carcinoma in one case and suspected carcinoma in two cases. The cytologic diagnosis was confirmed by core biopsy, and by post-operative histology in the malignant lesions. The remaining 10/14 (71%) cytologic samples were inadequate for diagnosis. All the microhistologic samples (100%) were considered sufficient for diagnosis and yielded diagnosis of benignity in 9/14 (60%) lesions and malignancy in 5/14 (40%). Two patients with benign diagnosis underwent surgery, which confirmed the diagnosis. The remaining seven patients were evaluated by follow-up MRI; the first follow-up at 3 months showed no significant changes. Post-operative histology of the 5 lesions with malignant microhistologic diagnosis confirmed the nature of the lesions.

MR-guided stereotactic biopsy is a simple, fast and safe procedure comparable to the interventional breast procedures performed under mammography and ultrasound guidance. The stereotactic device used ensures correct positioning of the needle into the lesion. The new dedicated non-magnetic needles and the mixed kit provide quantitatively and qualitatively adequate tissue for the histologic analysis. On the basis of our initial experience, we conclude that the procedure is feasible and accurate and can therefore be recommended for routine clinical use.