Synchronous unilateral triple breast cancers composed of invasive ductal carcinoma, invasive lobular carcinoma, and Paget's disease.

We report a case of synchronous unilateral triple breast cancers comprising invasive ductal carcinoma (IDC), invasive lobular carcinoma (ILC), and Paget's disease. A 57-year-old woman with a left breast mass was referred to our hospital. Mammography revealed only an isodense area with foci of microcalcification in the lateral area of the left breast. Ultrasonography revealed 2 hypoechoic masses in the outer lower and inner upper areas, and these 2 lesions were diagnosed by core needle biopsy as ILC and IDC, respectively. Left total mastectomy with sentinel lymph node biopsies was performed. In addition to the ILC and IDC, histological examination also identified Paget's disease. Breast cancer often manifests as multiple unilateral lesions; however, it is sometimes difficult to determine whether these tumors have developed multicentrically or have multifocally invaded from an intraductal carcinoma. This case was clearly diagnosed to have occurred multicentrically because of the absence of continuity among the 3 tumors, the presence of a non-invasive component in all 3 tumors, and different histopathological findings. The synchronous unilateral development of ILCs is well known. Cases of synchronous unilateral triple or more breast cancers were reviewed, and their histopathological characteristics, including the incidence of Paget's disease, is discussed.