Preoperative MRT of the breast in invasive lobular carcinoma in comparison with invasive ductal carcinoma

Purpose: To evaluate the role of preoperative MRI of the breast in invasive lobular carcinoma (ILC) compared to invasive ductal carcinoma (IDC). Materials and Methods: For one year, all patients transferred by the hospital's gynecologic outpatient service for suspicious findings in routine mammography and/or ultrasound (conventional modalities = CM) underwent preoperative MRI of the breast. Retrospective analysis of the histologic findings identified 17 patients with ILC. These were compared with 30 proven IDC patients, chosen by random. The MRI findings of these 2 patient groups were compared with regard to the detection of additional lesions. The average number of additional lesions detected by MRI was compared for significant differences between both groups using the T-test for paired samples. Results: In the 17 patients with ILC, conventional modalities (CM) identified 21 malignant lesions whereas MRI detected a total of 30 lesions. At least one additional lesion was detected by MRI in 7 of the 17 patients with ILC. In the 30 patients with IDC, on the other hand, MRI detected an additional lesion in three instances only. In one patient of the ILC group, MRI identified an additional lesion in the contralateral breast that had escaped detection by CM. No additional contralateral lesion was detected by MRI in any of the IDC patients. Benefit of MRI in ILC-Group: The mean numbers of detected malignant lesions differed significantly between diagnosis by MRI and CM in the ILC group (1.77 carcinomas per patient with MRI versus 1.24 with conventional modalities, T-test, p = 0.0078). Benefit of MRI in IDC-Group: although it was possible to find 1.27 carcinomas vs. 1.17 carcinomas per patient in the IDC-Group, this benefit was not statistical significant (T-test, p = 0.0831). Conclusion: Preoperative MRI detects multiple additional lesions compared to the ones already known by CM. The higher incidence of multiple lesions in ILC compared to IDC and the difficult diagnosis of ILC in CM might be the reason for the fact that preoperative MRI is particularly useful in patients with ILC.