Triple-negative breast cancer: MRI features in 29 patients.

Triple-negative (TN) breast cancers were defined as those which tested negative for estrogen receptor (ER), progesterone receptor (PR), and HER2. TN breast cancers account for 12%– 26% of all types of breast cancers [1–5]. TN tumors were aggressive and were usually diagnosed at a later stage [5]. About 85% of TN phenotypic breast cancers are deemed to be basal like and have a clinical behavior similar to basal-like tumors [2]. The most common histological types for TN breast cancer were invasive ductal carcinomas and metaplastic carcinomas [2]. Histologically, TN cancers are poorly differentiated, mainly of high histologic grade and with high mitotic index [1, 6]. Imaging features of this clinically important subtype of breast cancer are not well known. This study aimed to analyze its magnetic resonance imaging (MRI) features. In a full review of our breast MRI database from 2002 to 2006, 29 pathologically proven TN breast cancer patients (25–82 years old, mean 50, median 46) were analyzed. Twentyfive patients (25/29, 86%) were diagnosed with pure invasive ductal carcinoma and four patients (14%) with metaplastic breast cancer, including three with ductal and squamous components and one with ductal and chondroid components. The MRI study was carried out on a 1.5-T Phillips Eclipse magnetic resonance (MR) scanner with a standard bilateral breast coil (Philips Medical Systems, Cleveland, OH). After mid-2005, nine patients also received single-voxel proton MR spectroscopy, using point-resolved spectroscopic (PRESS) sequence for the correct localization of the volume of the centered lesion of interest, for detection and quantification of choline. The imaging protocol consisted of precontrast sagittal spin echo T1-weighted imaging and dynamic contrastenhanced axial 3D SPGR (RF-FAST) T1-weighted imaging. The sequence was repeated 16 times, four pre-contrast, and 12 postcontrast sets after injection of Omniscan (1 cc/10 lbs body weight). After the dynamic scan was completed, subtraction images and the maximum intensity projections (MIPs) were generated for tumor size measurements. The enhancement kinetics curves were analyzed from areas showing the brightest enhancement in the lesion. The lesion morphology and enhancement kinetic features were defined according to the Breast imaging reporting and data system atlas published by the American College of Radiology (BI-RADS atlas or ACR BIRADS lexicon) [7]. The morphologic criteria included masstype lesion [focus/foci (<5 mm), mass (>5 mm)] and non-mass type of enhancement (focal area, linear, ductal, segmental, regional, multiple regions, and diffuse enhancement). The evaluation of enhancement kinetic curve was on the basis of initial (within the first 2 min or when the curve starts to change), and late phases (after 2 min or after the change). The presence of abnormal skin enhancement of the breast and associated axillary lymph nodes were also recorded. A radiologist with 2 years’ experience interpreting breast MR analyzed the MR imaging features. Table 1 shows the demonstrated MRI features in these 29 patients. One patient had bilateral breast cancer and six patients (21%) had multiple cancer foci in the same breast. Tumor size ranged from 4 mm to 10 cm (4.1 6 2.7 cm). The average tumor size was much bigger than the non-TN-type breast cancer. Twenty-seven patients (27 of 29 patients, 93%) had tumor >1.5 cm, and 10 patients had tumor <5 cm with prominent skin enhancement (34%), which raised the suspicion of T4 stage with dermal lymphatic invasion (Figure 1). Overall, six patients (21%) were T1 stage, 12 (41%) were T2, and 11 (38%) were T3 or above. This is consistent with the findings of Haffty et al. [1] and Rakha et al. [2] reporting that TN tumors were larger (>1.5 cm) or had a higher T staging than non-TN tumors (79% versus 62%, 42% versus 21%, respectively). Except for one patient presenting with a non-mass type of regional enhancement, the other 28 patients (97%) had mass-type lesions. Twenty-six of the 28 mass-type lesions (93%) were >1.5 cm and showed strong and/or heterogeneous enhancements. Rim enhancement, a specific sign of malignancy on breast MRI, was identified in 12 patients (41%). Twenty-two lesions had documented enhancement kinetic curves, and all showed the typical malignant kinetic feature with rapid up-slope followed by washout (100%). The morphological and kinetics features are in accordance with MRI features of invasive ductal carcinoma. Fourteen patients (14 of 29 patients, 48%) showed identifiable lymph nodes in the axillary region. It was reported that in the TN and non-TN tumors with the same positive nodal status, the 5-year nodal relapse-free rate was significantly different between the two groups and the TN subtype was more