Magnetic resonance imaging facilitates breast conservation for occult breast cancer

Occult primary breast cancer, i.e., isolated axillary adenocarcinoma withou t detectable tumor in the breast by either physical exam or mammography, re presents up to 1% of operable breast cancer. Modified radical mastectomy (M RM) is generally the accepted treatment for this condition although tumor i s identified in only two-thirds of mastectomy specimens. Breast magnetic re sonance imaging (MRI) can identify occult breast carcinoma and may direct t herapy. This study examined the ability of breast MRI to detect occult brea st cancer and to facilitate breast conservation therapy. Methods: Forty women with biopsy-proven metastatic adenocarcinoma to an axi llary lymph node and no evidence of primary cancer were studied. All patien ts had a physical examination, mammography, and MRI of the breast. Using a dedicated breast coil, MRI imaging was performed with and without gadoliniu m enhancement. Positive MRT scans were compared with histopathologic findin gs at the time of operation (n = 21). Results: MRI identified the primary breast lesion in 28 of 40 women (70%). Of these 28 patients, 11 had MRM, 11 had lumpectomy/axillary lymph node dis section (ALND)/radiotherapy (XRT), 2 had ALND/XRT alone, and 4 had no local treatment secondary to stage IV disease. Two women initially treated with lumpectomy/ALND subsequently had mastectomy for positive margins. Of the wo men with positive MRI who had breast surgery, 21 of 22 (95%) had tumor with in the surgical specimen. Twelve women had negative MRI of the breast. Five of these 12 underwent MRM, of whom 4 had no tumor in the mastectomy specim en. The remaining 7 patients had ALND and whole breast radiation (ALND/XRT) (n = 5), or were observed (n = 2). Overall, 18 of 34 women surgically trea ted had MRM, while 16 (47%) preserved their breast. Tumor yield for patient s having breast surgery was 81%. Conclusions: MRI of the breast can identify occult breast cancer in many pa tients and may facilitate breast conservation in select women. Negative bre ast MRI predicts low tumor yield at mastectomy.