Final answer:
The most common cause of bloody nipple discharge is intraductal papilloma, followed by fibrocystic changes in the breast tissue. DCIS is less common. Accompanying symptoms should always be considered for potential broader medical conditions.
Step-by-step explanation:
The most common cause of bloody nipple discharge is an intraductal papilloma, which is a small, benign tumor located within a milk duct in the breast. The second most common cause is fibrocystic changes, which are benign changes in the breast tissue that can cause cysts and discomfort. Unlike intraductal papilloma, fibrocystic changes can lead to a variety of symptoms, which may include lumps or a thickening of the breast tissue, and tenderness especially related to the menstrual cycle. Ductal carcinoma in situ (DCIS), a non-invasive breast cancer, can sometimes present with nipple discharge but is less common. When answering clinical questions it is important to consider other symptoms that may accompany the primary concern, like unusual lumps, persistent indigestion, changes in warts or moles, and chronic cough or hoarseness that can suggest broader medical conditions.