Intraductal Papilloma: This is the most common cause of bloody nipple discharge. It is a benign tumor that grows in the milk ducts of the breast and can cause bleeding, leading to bloody discharge.

Ductal Carcinoma In Situ (DCIS): A type of non-invasive breast cancer that can cause bloody nipple discharge. It is less common than intraductal papilloma but more serious due to its potential to progress to invasive cancer.
Breast Cancer: Invasive breast cancer can also cause bloody nipple discharge, although it is less common. The discharge may be accompanied by other symptoms like a lump or changes in the breast skin.
Periductal Mastitis: An inflammatory condition that affects the ducts under the nipple. It can cause bloody discharge, nipple retraction, and periareolar abscesses.

Paget's Disease of the Breast: A rare form of breast cancer that affects the skin of the nipple and, sometimes, the areola. It can cause bloody discharge, along with other symptoms like itching, redness, and a rash.
Inflammatory Breast Cancer: A rare and aggressive form of breast cancer that can cause rapid changes in the breast, including redness, swelling, and warmth. Bloody nipple discharge can be a symptom, although it is not the most common presentation.

Breast Hemangioma: A benign vascular tumor that can cause bloody nipple discharge, although this is very rare.
Tuberculosis of the Breast: A rare condition where tuberculosis infects the breast tissue. It can cause a variety of symptoms, including bloody nipple discharge, although this is uncommon.
Sarcoidosis of the Breast: A condition where granulomatous inflammation affects the breast. It can cause bloody nipple discharge among other symptoms, but this is extremely rare.