Incidentally Detected Breast Lesions on Computed Tomography: Comparison with Mammography and Ultrasound

Abstract

Objectives:

To determine the reliability of incidentally detected breast lesion on CT scan compared with mammography and ultrasound.

Methods:

The study group is consisted of 39 patients (49 breast lesions), who incidentally found breast lesions from chest or abdomen CT scan.  The study was retrospectively reviewed CT features (size, shape, margin, density and enhancement pattern) and mammography with ultrasound features and categorized into American College of Radiology Breast Imaging Reporting And Data System (ACR BI-RADS). The comparison of ACR BI-RADS from CT scan and mammography with ultrasound was made by Kappa test to evaluate the agreement. Results: There was substantial agreement (k = 0.741, 95% CI 0.594-0.887) between CT and mammography with supplementary ultrasound findings. Mass lesions were found 46 in 49 lesions, macrocalcifications without mass 2 lesions and non-mass lesion 1 lesion (total 49 lesions). 

Most common shape of breast lesion from CT scan was oval shape seen 36 in 46 lesions ( 78.3%). Most common margin was circumscribed seen 38 in 46 lesions (82.6%). Iso-density lesions were seen 18 in 26 lesions ( 69.3%), 3 hyperdense lesions (11.5%) and 4 hypodense dense lesions ( 15.4%) and one fat-containing lesion ( 3.8%). Hounsfield unit (HU) study is between -50 to 61 HU ( mean 27.1).  Homogeneous enhancement were seen 27 in 44 lesions ( 61.4%) , non-enhancement pattern of 12 lesions (27.2%). Four non-enhance lesions were recognized as cysts due to low attenuation (< 20 HU) There were 11 lesions containing internal calcification, most of which were macrocalcification seen 9 in 11 lesions ( 81.8%). Overlying skin and nipple involvement were observed 2 in 49 lesions ( 4.1%). Lymphadenopathy and chest wall invasion were found in one case ( 2.0%).

Conclusions:

CT was rather good for evalulation of shape and margin of breast masses, while density value, enhancement pattern and calcification show non-specific results. ). Moreover, contrast enhanced CT scan has rather good reliability for diagnosis of benign lesion (BI-RADS 2) and malignant lesion (BI-RADS 5). However, for interpretation of suspicious lesion (BI-RADS 4) , it should be interpreted cautiously and compared with mammography and ultrasound due to over diagnosis in CT in this group.