Abstract P4-01-17: Ductolobular breast carcinoma and the role of preoperative magnetic resonance imaging

Abstract

Abstract Introduction: Lobular carcinoma is the second most frequently diagnosed type of invasive breast cancer (about 10%) after the ductal NOS type (80%). In patients with lobular carcinoma, magnetic resonance imaging (MRI) plays an important role in the pre-operative work up, since mammography and ultrasound often underestimate the tumor extent and have a high false negative rate for additional foci in the ipsi- or contra lateral breast when compared to MRI. As the histological spectrum of invasive breast cancers is however a continuum with gradual transitions between types, mixed type invasive carcinomas with both ductal and lobular histologic features occur and are usually denoted ductolobular cancer. In our institution, MRI is part of the routine pre-operative work up in patients with ductolobular breast cancer, but the value of MRI in the pre-operative work up of ductolobular carcinoma has yet to be determined. Purpose: We set out to determine the probability of detecting additional, clinically relevant, findings on MRI in patients diagnosed with ductolobular carcinoma. Methods: We retrospectively searched the pathology database for all patients diagnosed with histologically proven ductolobular breast cancer at our institution between 2008-Sept 2012. Findings on mammography and ultrasound were compared with the findings on the pre-operative MRI. Additional findings on MRI (larger tumor size, additional ipsi- and contralateral lesions) were verified by pathology evaluation. Results: Out of the 121 patients diagnosed with ductolobular cancer, 91 (75%) underwent MRI for pre-operative work-up. With MRI, 67 additional findings were detected in 56 (62%) patients. In 23 patients a contralateral additional lesion was seen, of which 12 turned out malignant. Ipsilateral lesions were seen in 28 patients, 20 of which were malignant at histology. In 16 patients, more extensive disease was seen on MRI compared to conventional imaging (mean difference was 18 mm, range 6–67 mm). MRI correlated better with the histological extent of these tumors (r = 0.97) than conventional imaging (r = 0.79). Of all MRI detected additional findings, 69% (46/67) was proven malignant after histology assessment. On patient-level, MRI led to the detection of one or more malignant finding(s) in 41/91 (45%) patients. Conclusion: For patients diagnosed with invasive ductolobular breast cancer, the probability of detecting clinically relevant additional findings on MRI is high. Preoperative MRI should therefore be part of the routine work up of this breast cancer type. Citation Information: Cancer Res 2012;72(24 Suppl):Abstract nr P4-01-17.