A Case of Invasive Ductal Carcinoma Occurring in a Breast Fibroadenoma

Abstract

A 41-year-old woman had a breast mass in her left upper quadrant. Mammography revealed grouped, round-shaped microcalcification (category 3) in her left breast. A core needle biopsy was performed and diagnosed as an invasive ductal carcinoma in a fibroadenoma. We performed left partial mastectomy and sentinel lymph node biopsy. Pathological examination revealed an invasive ductal carcinoma that grew within a 15 × 15 × 5 mm fibroadenoma, which was an estrogen receptor-positive, progesterone receptor-positive, HER2-negative, and low (<10%) Ki 67 cancer. Postoperative radiotherapy was performed for her left breast, and she is currently receiving tamoxifen therapy. Breast cancer within a fibroadenoma is rare. This is the 17th case report in the Japanese literature. Thus, we report a case of invasive ductal carcinoma occurring in a fibroadenoma.