A 34-year-old nulliparous woman presents to the clinic with 2 weeks of copper-colored discharge from her right nipple. Her breast has not been tender, and she has not noticed any changes to the skin. She is otherwise healthy and does not take any medications. Her temperature is 36.5°C (97.7°F), blood pressure is 110/82 mmHg, pulse is 68/min, respirations are 12/min, and oxygen saturation is 99% on room air. Exam of the right breast reveals no mass on palpation. Bloody discharge is expressed from the right nipple. There is no axillary lymphadenopathy. Which of the following is the most likely diagnosis?
Ductal carcinoma in situ
Mammary duct ectasia
Invasive ductal carcinoma
Intraductal papilloma
Intraductal papilloma
This young patient who presents with non-painful unilateral bloody nipple discharge and no palpable mass on breast exam most likely has an intraductal papilloma.

Intraductal papilloma is a benign epithelial tumor that develops in the lactiferous ducts of the breast and is the most common cause of bloody nipple discharge in premenopausal women. Patients typically present with painless unilateral bloody nipple discharge, and often there is no mass palpable on breast exam. Ultrasound is the initial method for evaluation and may reveal an intraductal mass, but if results are inconclusive, further imaging with mammography is indicated. If the results of both still remain inconclusive, galactography (radiography after injecting radiopaque contrast into the duct system) is the most accurate imaging method for diagnosing intraductal papilloma. A core biopsy of the intraductal mass should be obtained, and if results show papilloma with atypia, treatment would be surgical excision of the involved duct to rule out a concomitant malignant neoplasm.

Khan et al. review the treatment of intraductal papilloma and note that in lesions with core biopsy showing papilloma with atypia, surgical excision revealed the diagnosis of a concomitant invasive or ductal in situ cancer is common. The authors also find that in patients whose core biopsies showed papilloma without atypia, the likelihood of cancer was much lower. The authors recommend that since the diagnosis of intraductal papilloma carries an increased risk of breast cancer compared to the general population, these patients should be monitored accordingly.

Incorrect Answers:
Answer A: Ductal carcinoma in situ (DCIS) is a neoplastic lesion confined to the breast duct that if untreated develops into invasive ductal carcinoma. Typically, patients are asymptomatic, and lesions are detected via screening mammography. Though it can sometimes present with nipple discharge, this is less common. Unilateral painless bloody nipple discharge is more likely to be due to intraductal papilloma, though no mass may be palpable for either diagnosis.

Answer C: Invasive ductal carcinoma is the most common type of breast cancer, which typically presents as a firm, immobile, painless lump in the breast, sometimes associated with nipple discharge, overlying skin changes, inverted nipple, and/or axillary lymphadenopathy. As with DCIS, nipple discharge may be present but is usually not bloody as in cases of intraductal papilloma.

Answer D: Mammary duct ectasia is a benign condition in which a milk duct in the breast widens and its walls thicken, leading to blockage and build-up of fluid in the duct. This is usually asymptomatic but can present with off-white or greenish nipple discharge. It may also result in infection of the affected duct, leading to periductal mastitis and a tender, erythematous breast. It tends to occur in perimenopausal women and often resolves without treatment, though if symptoms persist it can be treated with antibiotics and duct excision.

Answer E: Paget disease of the breast often presents as a scaly, raw, vesicular, or ulcerated lesion that begins on the nipple and then spreads to the areola, sometimes associated with bloody nipple discharge. Pain, burning, and pruritis are also common presenting symptoms. There is often an underlying breast carcinoma; thus, any patient with Paget disease should be evaluated with a mammogram. Although this patient has bloody nipple discharge, she does not present with a painful, scaly, raw, or vesiculated lesion that would be concerning for Paget disease of the breast.

Bullet Summary:
Intraductal papilloma often manifests in patients as painless unilateral bloody nipple discharge, and typically no mass is palpable on exam.