Two Cases of Intraductal Papilloma with Sebaceous Metaplasia of the Breast

INTRODUCTION: Intraductal papilloma is a common benign breast lesion that typically presents with nipple discharge or a palpable mass. While apocrine metaplasia is frequently observed, sebaceous metaplasia is very rare in breast lesions, with only a few cases reported to date. We herein describe two surgically resected cases of intraductal papilloma with sebaceous metaplasia, both of which were histologically proven benign following imaging findings that were suspicious for malignancy. CASE PRESENTATION: Case 1: A 47-year-old woman presented with a left breast mass detected during routine screening. Imaging revealed an intracystic lesion with mural nodules and features that were suspicious for malignancy. Surgical excision was performed, and a histopathological examination confirmed intraductal papilloma with sebaceous metaplasia. Case 2: A subareolar mass was detected in a 62-year-old woman during screening ultrasonography. Cytology showed atypical features suspicious for malignancy. Surgical resection yielded a diagnosis of intraductal papilloma with sebaceous metaplasia. CONCLUSIONS: These cases represent rare occurrences of intraductal papilloma with sebaceous metaplasia, an entity for which only one case has been reported in the English literature and lacked imaging documentation. Our results highlight characteristic imaging features, such as cyst wall thickening and solid internal components with marked enhancement, which may mimic malignancy. These findings provided new insights into the imaging and pathological spectrum of metaplastic changes in intraductal papilloma. Recognition that sebaceous metaplasia can occur within an otherwise benign papilloma may help avoid overinterpretation of suspicious imaging findings and contribute to more appropriate clinical decision-making.