Background: Nipple adenoma (NA) is a rare benign tumor arising in the lactiferous ducts of the nipple. It typically presents as a palpable nodule, erosion, or discharge with erythema of the nipple. NA is different from other mammary proliferative diseases of the nipple; however, its clinicopathologic characteristics have been scarcely elucidated. Objective: In this study, we aimed to assess the clinical and histopathological characteristics of NA and compare them with mammary Paget’s diseases and breast carcinomas of the nipple. Methods: We retrospectively reviewed fifteen patients with NA. Furthermore, we reviewed fifteen patients with nipple Paget’s diseases and five patients with breast carcinomas (ductal carcinoma in situ and invasive ductal carcinoma). Skin lesions’ clinical characteristics and general histopathological findings were investigated. Results: NA showed significantly early onset (p=0.014), delayed time for onset to diagnosis (p=0.026), and smaller lesion than other nipple malignant diseases (p＜0.001). NA was predominantly localized on the right side and exhibited as more palpable mass and less nipple discharge as initial symptoms. Estimated prevalence of Korean cases (0.026%) was twice higher than Western countries (0.012%). p16 immunostaining in NA and other malignant diseases did not differ. Conclusion: NA is a benign neoplasm arising on the nipple. NA showed earlier onset with smaller size at initial presentation than other malignant diseases which presented more crusts. Unnecessary surgical procedures for NA should be avoided with preceding clinical differential diagnosis. (Korean J Dermatol 2022;60(1):35∼43)