Incidental detection of clinically unexpected breast lesions by computed tomography

Abstract

Background Increased use of computed tomography (CT) has resulted in greater detection of incidental breast lesions unrelated to the primary diagnostic inquiry. Purpose To investigate the morphology and clinical significance of breast abnormalities detected incidentally by conventional CT. Material and Methods A total of 2945 female patients underwent CT examinations of the body, including the chest, from May 2006 to April 2010. Two radiologists interpreted these CT scans independently and pointed out a mass or non-mass-like lesion as abnormalities in the breast. Patients who incidentally showed breast lesions on CT scans were identified by a computer-based search of the diagnostic reports and were enrolled in this study. The morphology and enhancement patterns of CT-detected breast lesions were evaluated according to BI-RADS-MRI. Results In total, 32 clinically unexpected abnormal breast lesions were found in 31 (1.1%) patients. Twenty-nine of the 32 lesions were detected by contrast-enhanced CT and three by unenhanced CT. Ten breast cancers were found in 10 patients (0.34%), which yielded the prevalence for malignancy of 31% (10/32). Invasive ductal carcinomas accounted for eight lesions, while two were ductal carcinomas in situ (DCIS). Nine lesions were depicted as a mass and one DCIS was a non-mass-like lesion. Good morphological predictors of breast cancers for a mass were an irregular shape, a lobulated shape, and an irregular margin. Benign lesions accounted for 22 lesions from 21 patients (0.71%). Of these, 13 lesions in 13 patients were depicted as a mass and nine lesions in nine patients as a non-mass-like lesion. Conclusion Unexpected breast lesions can be identified as a mass or non-mass-like lesion on conventional chest CT scans. Among these, breast cancers that are not clinically apparent occur with considerable prevalence. We suggest that careful interpretation of the breast should be a routine part of CT examinations.