A lthough chest computed tomography (CT) usually covers the whole breast tissue, it is not the primary method for the evaluation of the breast. Chest CT has the drawback of exposing breasts to radiation. Inoue et al. (1) reported that the radiation dose at the skin surface of the breast during CT scanning was approximately ten times greater than the dose received during standard mammography.However, recent studies have reported the importance of chest CT for the detection of unexpected breast lesions (2-8). These breast lesions may include primary and secondary malignancies, as well as benign lesions, including benign calcification, fibroadenomas, and lipomas (2-4). Sometimes, CT may be the first modality to demonstrate a new primary breast cancer (5). In recent literature, the prevalence of breast cancers among incidental lesions detected using CT varied from 24% to even 70% (6-8). Therefore, it may be important for radiologists to pay attention to the breast during routine chest CT examinations.In this pictorial essay, we illustrate incidental breast lesions that are encountered while interpreting chest CT in our institution. For each lesion that was originally detected by CT, ultrasonography (US) findings are also presented.
Benign breast lesions
Fibrocystic changesThe term "fibrocystic changes" has been used to refer to various histologic conditions, ranging from normal physiologic changes to true premalignant proliferations of breast tissue (9). Imaging features of this condition are variable. US usually shows an iso-to hypoechoic solid nodule with a round or oval shape (10). To our knowledge, there have been no documented features of fibrocystic changes on CT. However, CT may reveal an oval or round mass that eventually requires biopsy (6) (Fig. 1).
FibroadenomaFibroadenomas are the most common benign breast tumors that occur during the reproductive period. In most cases, US shows an oval mass with circumscribed margin, hypoechogenicity, and parallel appearance (9). However, US findings may be variable, sometimes indistinguishable from cancer. On CT, fibroadenomas appear as either a calcified or noncalcified nodule with well-defined margins (2). Many fibroadenomas undergo hyalinization, calcification, and atrophy over time, although the relationship of these findings with menopause is unclear (9). When densely calcified, fibroadenomas exhibit a pathognomic appearance of popcorn-shaped large calcifications on both mammography and CT, which is representative of benign calcification (4, 9) (Fig. 2).
ABSTRACTWith the increasing use of computed tomography (CT), incidental breast lesions are detected more frequently. When interpreting chest CT findings, it is important for radiologists to carefully review the breast to recognize any abnormal findings that could affect patient management. The purpose of this study is to discuss incidental breast lesions on chest CT with ultrasonography correlation that may be encountered in routine clinical practice.
