Support. Source says " Pathologic nipple discharge is spontaneous and often unilateral. It may arise from a single duct or be associated with a mass or new skin changes. It can be bloody, serous, green or black.1–3 Benign intraductal papilloma (48%), ductal ectasia (15%–20%) and carcinoma (10%–15%) are the most common causes.1." Clearly saying intraductal papilloma is most common pathologic cause, not most common overall. Other sources cited by UW agree.
Added accepted-suggestion, #deck-AnKing Overhaul for Step 1 & 2-AnKingMed and removed #deck-anking-overhaul-for-step-1–2-ankingmed, open-suggestion