Ductal carcinoma in situ arising in tubular adenoma of the breast

We herein report an extremely rare case of ductal carcinoma in situ (DCIS) arising in tubular adenoma of the breast. A 33-year-old female first noticed a mass in her right breast when she was 15 years old. The tumor had not changed in size subjectively for 18 years. She finally visited the hospital one and a half years before this presentation for an examination of her breast mass. Ultrasonography (US) showed a circumscribed mass suggesting a benign tumor, and mammography (MMG) revealed the well-defined high-density mass with a focal region of microcalcification. It was suspected to be adenosis based on a core-needle biopsy (CNB). During the regular follow-up, the microcalcification in the mass increased. She was therefore referred to our hospital for further examination. US and MMG showed a well-demarcated mass with a focal microcalcified area. US-guided CNB diagnosed it as DCIS with tubular adenoma. The patient underwent tumorectomy. Histologically, the tumor was diagnosed to be DCIS in tubular adenoma with negative surgical margins.