Unusual Sonographic Finding of Metastatic Invasive Lobular Carcinoma to the Contralateral Breast

Invasive lobular carcinoma (ILC) is the second most common breast cancer after invasive ductal carcinoma (IDC), accounting for 5% to 14% of all breast cancers.1 Like other primary breast cancers, ILC can metastasize to a contralateral breast via lymphatic or hematogenous dissemination. However, contralateral breast cancer metastasis is a rare event. A variety of sonographic findings of metastases from extramammary malignancies have been reported, 2 but those from contralateral breast cancer are little known. We report an unusual sonographic finding of contralateral metastases of ILC in a patient with advanced breast cancer and systemic metastases.