A 45-year-old, nulligravid woman comes to the office for intermittent nipple discharge. For the past month, the patient has had spontaneous discharge from her left breast. She has felt no breast masses or breast pain, but she did have trauma to the breast from a skiing accident 3 months ago. Review of systems is otherwise negative. The patient has hypothyroidism for which she takes levothyroxine. Family history is unremarkable. She does not use tobacco, alcohol, or illicit drugs. Blood pressure is 126/82 mm Hg and pulse is 70/min. BMI is 28 kg/m². Physical examination shows no palpable breast masses. There is dried blood on the left nipple, and a serosanguineous discharge is expressed. Examination of the right breast is unremarkable. There is no axillary lymphadenopathy. Mammography shows no masses or calcifications. Which of the following is the most likely cause of this patient's presentation?

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11ec25c8_d894_a5cd_bc81_971cb7be92a0_MD0003_00 Nipple discharge is a common breast condition and classified as either physiologic (ie, galactorrhea) or pathologic (ie, concerning for malignancy). Pathologic nipple discharge includes discharge that is unilateral, bloody, spontaneous, or associated with other breast abnormalities (eg, palpable mass, skin changes). The most common (~50%) cause of unilateral bloody nipple discharge without a coexisting breast mass or lymphadenopathy is an intraductal papilloma. Intraductal papillomas originate from the breast duct lining and are typically nonpalpable due to their small size (≤1 cm) and intraductal location. Intraductal papillomas Although this benign condition is the most likely diagnosis, bloody nipple discharge can also be a sign of underlying breast cancer (eg, invasive ductal carcinoma) caused by tumor growth into the lactiferous duct system. Therefore, patients with pathologic nipple discharge require breast imaging with either ultrasound (age <30) or mammogram plus ultrasound (age ≥30). With small intraductal papillomas, mammography is often normal due to low sensitivity for ductal pathology; however, ultrasound may demonstrate a dilated duct due to the space-occupying papilloma. (Choice A) Although intraductal papillomas can contain foci of ductal carcinoma in situ (DCIS), 90% of patients with DCIS have microcalcifications seen on mammography. This patient's mammogram is normal. (Choice B) Ductal ectasia (ie, benign breast duct thickening and dilation) can lead to bloody nipple discharge as the duct widens. However, ductal thickening typically clogs the duct, resulting in a buildup of fluid, overlying skin erythema, and nipple pain, which are not seen in this patient. (Choice C) Fat necrosis of the breast is a benign condition caused by breast trauma. It typically presents as a firm, palpable, irregularly shaped mass. Nipple discharge is uncommon. (Choice E) Paget disease of the breast, a form of ductal carcinoma, can cause unilateral bloody nipple discharge due to intraductal tumor growth or necrosis. However, patients typically have eczematous nipple or skin changes (eg, flaking, crusting skin). Paget disease of the breast (Choice F) Poorly controlled hypothyroidism stimulates the hypothalamic release of thyrotropin-releasing hormone, which increases both TSH and prolactin release by the anterior pituitary. Increased prolactin levels can cause physiologic nipple discharge (ie, galactorrhea), which is typically bilateral and milky rather than unilateral and serosanguinous. Educational objective: The most common cause of unilateral, bloody nipple discharge is a benign intraductal papilloma. Patients with an intraductal papilloma typically have no associated breast mass or lymphadenopathy; mammography is usually normal. References: Nipple discharge: the role of imaging. (http://www.ncbi.nlm.nih.gov/pubmed/26433322) Nipple discharge. (http://www.ncbi.nlm.nih.gov/pubmed/25733736) Common breast problems. (http://www.ncbi.nlm.nih.gov/pubmed/22963023)

A 45-Year-Old, Nulligravid Woman Comes to the Office for Intermittent