A Case of Breast Cancer Arising From a Florid Adenosis Nodule.

A 42-year-old woman noticed a left breast mass and was diagnosed with florid adenosis by vacuum-assisted biopsy (VAB) 10 years before. Semiannual ultrasound follow-ups showed gradual shrinkage of the florid adenosis nodule as time passed after VAB, but showed a slight increase in size after her marriage at the age of 40. Thereafter, the sudden rapid growth of the nodule made us again examine it in detail. Magnetic resonance imaging of the masses, including a daughter nodule in the nipple direction, showed low signals on T1-weighted images, slightly high signals on fat-suppressed T2-weighted images, and persistent rim enhancement on subtraction images. The patient underwent core needle biopsy under the tentative diagnosis of breast cancer. Pathological study showed atypical cells growing in a papillary fashion with bleeding and necrosis, leading to the diagnosis of invasive ductal carcinoma. Immunostaining showed estrogen and progesterone receptor negativity, human epidermal growth factor receptor type 2 negativity, and a high Ki-67 labeling index of 60%. The patient, therefore, underwent nipple-preserving mastectomy and sentinel biopsy followed by immediate breast reconstruction using an extended latissimus dorsi musculocutaneous flap. Postoperative pathological study showed that the breast cancer had similar pathological findings to those of the core needle biopsy specimen and a higher Ki-67 labeling index of 70%. The patient recovered uneventfully and was discharged on the 9th day after the operation. The patient has received dose-dense chemotherapy and is scheduled for periodical checkups on an outpatient basis. Breast specialists should note that even pathologically proven florid adenosis nodules might develop breast cancer.