Apparent ipsilateral decrease in breast size at mammography: a sign of infiltrating lobular carcinoma.

Abstract

To assess if infiltrating lobular carcinoma (ILC) is associated with an ipsilateral mammographic decrease in breast size. Mammographic change in size was evaluated by measuring the distance from the nipple to the pectoralis major muscle on the mediolateral oblique view of the diagnostic mammogram and on a preceding mammogram in 30 patients with ILC. Clinical, mammographic, and histopathologic findings were retrospectively reviewed. Five patients (17%) had an ipsilateral decrease in mammographic size. No patients noticed a physical decrease in breast size. Patients with an ipsilateral decrease in mammographic size most commonly had breast thickening at examination (four of five patients [80%], P < .001) and either a focal asymmetry density (three of five patients [60%]) or architectural distortion (one of five patients [20%]) at mammography; those patients with no change in size most commonly had a palpable mass (six of 25 patients [24%]) or normal findings (19 of 25 patients [76%]) and a mass (13 of 25 patients [52%]) at mammography. The mean tumor size was 66 mm for those with an ipsilateral size decrease and 16 mm for those with no size decrease (P < .001). At histologic analysis, tumors associated with an ipsilateral decrease in mammographic size had more diffuse involvement of the breast, and discrete masses were not seen. An apparent decrease in mammographic size may help identify cases of ILC, especially when associated with thickening at clinical examination and focal asymmetric density at mammography.