Ectopic ACTH secretion in the setting of breast cancer is extremely rare but when present affects both the tumor's behavior and the incidence of complications. The patient, a 58-year-old woman, first presented with a mass in her left breast as well as multiple osseous metastases and a right femur fracture. Laboratory data revealed a hypokalemic alkalosis. Her plasma ACTH level was elevated. She was diagnosed with breast cancer with ectopic ACTH secretion, and underwent a left mastectomy and axillary lymph node dissection. Histological examination demonstrated a poorly differentiated neuroendocrine carcinoma with ectopic ACTH secretion. Although the signs and symptoms of ectopic ACTH secretion from a breast cancer are frequently subtle, the recognition of ectopic ACTH secretion from breast cancer is important for patient management.
Keywords: adrenocorticotropic hormone; breast cancer; neuroendocrine cancer.