Contrast-enhanced CT evaluation of clinically and mammographically occult multiple breast tumors in women with unilateral early breast cancer

Background: Magnetic resonance imaging mammography is performed to determine the extent of lesions and to detect occult lesions, but preoperative diagnosis by breast computed tomography (CT) is less common. Methods: We performed a retrospective study of detection of mammographically occult multiple lesions using breast CT. The subjects were 407 female patients (median age: 56 years old; median tumor size: 1.9 cm) with breast cancer who underwent preoperative, contrast-enhanced breast CT. Results: CT detected 73 incidental-enhanced breast nodules (median size: 0.8 cm) in 73 patients that were undetectable by conventional methods. Age, size of the main lesion or laterality of lesions did not differ between patients with and without incidental nodules, but the frequency of mastectomy was significantly higher in those with incidental nodules. Of the 73 incidental nodules, 22 (30%;) were in the same quadrant as the main lesion, 26 (36%) were in other quadrants and 25 (34%) were in the opposite breast. On qualitative diagnosis by CT, 48 were suspected to be malignant (66%), 17 benign (23%) and eight non-specific (11%). In histological evaluation of 44 of the 48 nodules suspected to be malignant, 24 were malignant (invasive carcinoma: 22, non-invasive carcinoma: 2); of seven of the 17 nodules suspected to be benign, all were benign; and of three of the eight non-specific nodules, one was non-invasive carcinoma. The discovery rate of clinically and mammographically occult multiple lesions by preoperative breast CT was 6%. Conclusion: We conclude that breast CT is useful for the detection of occult lesions and choice of surgical procedure.