MR Imaging Findings of Infiltrating Lobular Carcinoma of the Breast

Abstract

Purpose: Invasive lobular carcinoma (ILC) is the second most common malign breast neoplasia. Its classic histological type presents a slow and insidious growth, but no exuberant desmoplastic reaction. Therefore, its clinical and radiological detection is challenging. All the predictive characteristics for malignancy in breast cancer on magnetic resonance (MR) imaging are well established in the literature. However, there are few studies examining the peculiar image aspects of less prevalent histological subgroups such as the pure ILC case. Therefore, this paper assesses the characteristics of MR imaging results from patients with a histologically confirmed diagnosis of pure ILC by comparing them to the characteristics classically described in the literature for breast cancer in general. Methodology: This document is an transversal study done on 43 female patients diagnosed with pure ILC who were treated at the Sirio-Libanes Hospital Mastology Center from January 2006 to August 2014 and who were subjected to pre-surgery and pre-biopsy MR examinations. Results: Lesions presented an average size of 3.2 cm (0,6-10,0 cm). The most common image aspect found was nodules with expansive growth pattern and irregular or spiculated margins. About 91% of patients showed nodules, and 9% showed only a non-mass enhancement (NME). Of patients with NME, the vast majority (77,7%) showed segmental distribution and 22.3% were the focal type. Enhancement kinetics with type I curves were found on 30.3% of lesions. The most prevalent curve type was type II (51.1%), while type III curves were only observed on 18.6% of lesions. In T2-weighted images, nearly half of the cases (41%) showed a distinct low-intensity signal on T2, while the rest showed iso-intense signal. No lesions showed a high signal on T2-weighted images. Other data, such as the presence of macrovascularization and signs of edema and distortion surrounding the tumor were less prevalent and were observed in less than a third of patients. Conclusion: In general, the image characteristics of pure ILCs imitate characteristics classically described for invasive breast cancer; however, a significant portion of ILC cases share less customary image characteristics including the presentation of nonmass enhancement and/or progressive enhancement, a distinct hypointense signal on T2-weighted images, and absence of macrovascularization or edema surrounding the tumor. Knowing these less customary aspects is an extremely important task– especially in cases where abnormalities are evidenced exclusively through MRI.