Differential Diagnosis for Greenish Discharge from Nipple

Single Most Likely Diagnosis

• Ductal Ectasia: This condition is characterized by the dilation of the milk ducts in the breast, often accompanied by a greenish or blackish discharge. It is a common cause of nipple discharge, especially in older women, and can be associated with periductal mastitis. The normal mammogram and ultrasound do not rule out ductal ectasia, as it may not always be visible on these imaging modalities.

Other Likely Diagnoses

• Intraductal Papilloma: These are small, benign tumors that grow in the milk ducts of the breast. They can cause a bloody or serous nipple discharge, but sometimes the discharge can appear greenish. While mammograms and ultrasounds are normal, these lesions are often small and might not be detected by standard imaging.
• Periductal Mastitis: This condition involves inflammation of the ducts under the nipple and can cause a variety of symptoms, including nipple discharge that may be greenish in color. It is more common in smokers and can be associated with ductal ectasia.

Do Not Miss Diagnoses

• Breast Cancer (especially Intraductal or Ductal Carcinoma In Situ): Although less likely, breast cancer can present with nipple discharge. It is crucial not to miss this diagnosis, as early detection significantly improves outcomes. The presence of a normal mammogram and ultrasound does not completely rule out cancer, especially if the discharge is from a single duct.
• Paget's Disease of the Breast: This rare form of breast cancer affects the skin of the nipple and, sometimes, the areola. It can cause eczema-like changes and might be associated with a nipple discharge. Given its potential for malignancy, it is a critical diagnosis not to miss.

Rare Diagnoses

• Galactorrhea due to Pituitary Tumor: Although galactorrhea (spontaneous milk production not associated with childbirth or nursing) is more commonly associated with a milky discharge, hormonal imbalances caused by pituitary tumors can lead to various types of nipple discharge, including those that might appear greenish.
• Fibrocystic Changes with Ductal Ectasia: While fibrocystic changes are common in the breast, when associated with ductal ectasia, they can cause a variety of symptoms, including nipple discharge. This condition might not always be distinguishable from other causes of discharge based on imaging alone.