Magnetic resonance mammography has limited ability to estimate pathological complete remission after primary chemotherapy or radiofrequency ablation therapy.

Recently, primary systemic chemotherapy has been used not only for locally advanced breast cancers but also for operable cases for which adjuvant chemotherapy is necessary. Moreover, various kinds of ablation therapies have been tried to treat early breast cancer non-surgically, such as radiofrequency ablation (RFA), interstitial laser surgery, cryosurgery and focused ultrasound surgery (FUS). If pathological complete remission (pCR) can be correctly assessed by magnetic resonance mammography (MRM) or ultrasonography (US), a non surgical approach can be used for treatment. MRM is now widely used to assess the effect of chemotherapy in the neoadjuvant setting. However, the ability of MRM to estimate pCR is not yet sufficient to allow a non-surgical approach to breast cancer. Conversely, ultrasonography (US) might over-diagnose fibrous change as residual invasive cancer. If both MRM and US reveal no abnormal finding, there might be no residual cancer on pathological examination. However, such circumstances are encountered in only 2-3% of cases given the neoadjuvant treatment. Other cases, such as US showing residual disease in spite of pCR on MRM, have some potential for false positivity. Therefore, US-guided needle biopsy, especially vacuum-assisted breast biopsy, might be suitable to judge whether true pCR was achieved in the targeted lesion.