Contralateral breast cancer adjacent to a fibroadenoma: report of a case.

A 64-year-old woman noticed a lump of the right breast and consulted our outpatient clinic. She had undergone multiple excisional biopsies of fibroadenomas in both breasts and mastectomy for invasive ductal carcinoma (IDC) of the left breast. After completing 5 years of treatment with adjuvant tamoxifen, she had undergone screening with annual physical examinations and occasional computed tomography. She was declared recurrence-free 13 years after breast cancer surgery, although lumps were detected in the right breast, probably due to fibroadenomas. Mammography, ultrasonography, and magnetic resonance imaging revealed that the lump was irregularly shaped, 2 cm in diameter, and adjacent to a fibroadenoma with macrocalcification. Two axillary lymph nodes were enlarged and suggestive of metastasis. A core needle biopsy revealed IDC of the right breast. She underwent a right partial mastectomy with axillary lymph node dissection. The IDC was 2 cm in diameter, of nuclear grade 2, and adjacent to a 0.7-cm fibroadenoma with a macrocalcification. The margins of the IDC close to the fibroadenoma were clearly demarcated by the fibrous capsule of the fibroadenoma. Four axillary lymph nodes were positive for metastasis. In the present case the presence of fibroadenoma might have interfered with the early detection of the contralateral IDC. The history of multiple excisions of fibroadenomas and mastectomy for breast cancer suggests an increased risk of contralateral breast cancer for the patient's entire life; therefore, regular annual follow-up, such as physical examinations and mammography, is recommended.