Study population
Our institutional review board approved this retrospective study, and the requirement for informed consent was waived. The database of our institution was retrospectively reviewed for image-guided biopsy and breast surgery occurring between January 2006 to December 2012 to identify patients with a diagnosis of radial scar/CSL with or without high risk lesions (i.e., atypical epithelial hyperplasia, lobular neoplasia, papilloma, or atypical papilloma). Radial scar was defined as a lesion of 1.0 cm or smaller, while CSL was defined as a lesion larger than 1.0 cm. We excluded patients who were initially diagnosed with ipsilateral breast cancer or those who were followed-up for a period of less than 5 years without having undergone surgery. Finally, we enrolled 82 radial scars/CSLs in 80 women; 51 were diagnosed by US-guided core needle biopsy, one by mammography-guided stereotactic biopsy, and 38 by surgical excision.
At initial diagnosis, 53 of the lesions were considered to be without high risk lesions and 29 lesions were considered as being accompanied by high risk lesions. Of the 53 radial scars/CSLs without high risk lesions, 37 lesions (69.8%) were surgically excised and 16 lesions (30.2%) were not excised but underwent imaging follow-up of at least 5 years. Of the 29 radial scars/CSLs with high risk lesions (15 atypical epithelial hyperplasia, 7 atypically papilloma, 7 papilloma), 27 lesions (93.1%) were surgically excised and two lesions (6.9%) were not excised but underwent imaging follow-up.
We recorded whether lesions were detected during screening or diagnostic examination, and whether patients were asymptomatic or symptomatic.
An upgrade was defined as occurring when the surgical pathology was changed from 1) a lesion without high risk to a high risk lesion, DCIS, or invasive carcinoma, and 2) from lesions with high risk to DCIS or invasive carcinoma.
Imaging technique and biopsy methods
Mammography was performed using a full-field digital mammogram unit (Senographe DS or Senographe Essential scanner, both from Generic Electric Medical System, Milwaukee, WI, USA). Two standard imaging planes were used, the mediolateral oblique and craniocaudal views.
Whole-breast US was performed using an IU22 unit (Philips Medical System, Bothell, WA, USA) equipped with a 50 mm linear array transducer with a bandwidth of 5–12 MHz. At our institution, the scanning technique for bilateral whole-breast US is standardized as follows: scanning is performed in a transverse and sagittal orientation, with the inner breast in a supine position and the outer breast in a supine oblique position with the patient’s arm raised above her head. The pectoralis muscle has to be seen on all images to ensure that the entire breast is examined. Each lesion is documented with an image of its longest dimension and an orthogonal measurement.
Dynamic contrast-enhanced MRI was performed on a 1.5 T scanner (Magnetom Avanto, Siemens Medical Solutions, Erlangen, Germany) using a dedicated 18-channel phased-array breast coil. The standard breast MRI protocol included the following pulse sequences: 1) an axial two-dimensional T2-weighted short tau inversion recovery (STIR) turbo spin-echo pulse sequence (repetition time/echo time/time interval (TR/TE/TI), 6700/74/150 ms; field of view (FOV) 300 × 300 mm; matrix size, 448 × 448; slice thickness, 5 mm); 2) pre and post-contrast-enhanced fat-saturated axial three-dimensional T1-weighted fast low angle shot volume interpolated breath-hold examination (FLASH VIBE) pulse sequences (TR/TE, 5.2/2.4 ms; FOV 340 × 340 mm; matrix size, 384 × 384; slice thickness, 0.9 mm). The six dynamic sequences (one unenhanced and five contrast-enhanced acquisitions with a temporal resolution of 59 s) were acquired before and after injection of contrast medium.
US-guided core needle biopsy was performed with a 14-gauge dual action semi-automatic core biopsy needle (Stericut with coaxial guide, TSK Laboratory, Tochigi, Japan), and a minimum of five core samples were obtained. Biopsies of mammographic findings such as asymmetry, architectural distortions, and calcifications without a corresponding US finding were performed with a stereotactic technique involving 11-gauge vacuum probes (Mammotome; Ethicon Endo-Surgery, Cincinnati, OH) on an upright stereotactic digital unit, using a Senographe Essential stereotaxic machine (General Electric Medical Systems, Milwaukee, WI).
All surgical excision was performed after US or mammography-guided wire localization, with specimen mammography being performed in cases of mammography-guided wire localization.
Analysis of imaging findings
Mammography, US, and MRI were retrospectively reviewed (without regard to the initial clinical reporting) by two radiologists with 6 and 17 years of clinical experience in breast imaging, respectively. Each radiologist was blind to the readings of the other radiologist. When a discrepancy occurred, the two radiologists reviewed the case together and reached a consensus. Imaging features were described and assessed according to the American College of Radiology (ACR) BI-RADS 5th edition [26].
On mammography, lesions were classified into mass, calcification, mass with calcification, architectural distortion, architectural distortion with calcification, and asymmetry. For a mass, the shape was described as oval, round, or irregular, and the margin as circumscribed, obscured, microlobulated, indistinct, or spiculated. For calcifications, the distribution was analyzed as diffuse, regional, grouped, linear, or segmental, and the morphology as amorphous, coarse heterogeneous, fine pleomorphic, or punctate.
On US, the shape of each mass was described as oval, round, or irregular; the orientation as parallel or non-parallel; the margin as circumscribed, indistinct, angular, microlobulated, or spiculated; and the echo pattern as anechoic, hyperechoic, complex cystic and solid, hypoechoic, isoechoic, or heterogeneous. Posterior features were classified as no posterior feature, posterior enhancement, posterior shadowing, or a combination. The visibility of any calcification on US was also assessed.
On breast MRI for mass lesions, the margins were described as circumscribed, irregular, or spiculated, and the shape as oval, round, or irregular. The internal enhancement of each mass was classified as homogeneous, heterogeneous, rim, or dark internal septation enhancement. For non-mass lesions, the distributions were described as focal, linear, segmental, regional, multiple regions, or diffuse, while the pattern of enhancement was classified as homogeneous, heterogeneous, clumped, or clustered ring. The enhancement kinetic curve was described as Type 1 (persistent enhancement), Type 2 (plateau), or Type 3 (peak early enhancement followed by delayed washout).
Statistical analysis
The characteristics of the patients and findings of the lesions, including upgrade rates, are summarized using number and percentage. Clinical characteristics and imaging findings were compared between lesions that underwent surgical excision (n = 64) and lesions that underwent follow-up (n = 18), with Student’s t-tests being used for continuous variables and χ2 tests for categorical variables. Lesions were also grouped according to the final pathological diagnosis (performed by surgical excision or follow-up of at least 5 years) as radial scar without high risk lesions (n = 49) or radial scar with high risk lesions (n = 33), and were compared using Student’s t-test or a Mann-Whitney test for continuous variables, and Fisher’s exact test for categorical variables. Calculations for statistical analyses were performed using SPSS software (version 23.0, IBM Corp., Armonk, NY, USA). A P-value of less than 0.05 was considered to indicate a statistically significant difference between groups.