A rare case of invasive ductal carcinoma with hyperprolactinemia.

We report here a rare form of invasive ductal carcinoma composed of a mass protruding from the tip of the nipple in a 43-year-old woman with hyperprolactinemia. She had been amenorrheic for 15 years following an incomplete pituitary adenomectomy for prolactinoma. She presented with a mass on the left nipple that had been growing for 6 months. Morphologically, the mass resembled adenoma of the nipple. Another mass was located in the subareolar region. She underwent mastectomy after invasive ductal carcinoma was diagnosed. Histopathologically, the tumor of the nipple was invasive ductal carcinoma, which had extended intraductally from another invasive ductal carcinoma in the subareolar region, and had infiltrated the epidermis of the nipple (Paget's disease). MR mammography successfully detected the relationship between the tumors. Postoperatively, the plasma prolactin level was abnormally high, while the plasma estradiol level was quite low, although macro-pituitary adenoma was not detected by MRI. The patient was treated with bromocriptine mesilate, in addition to adjuvant chemotherapy for breast cancer, and the plasma prolactin level has since normalized.