[A Case of Lobular Carcinoma In Situ Occurring in a Fibroadenoma of the Breast].

The patient was a 43-year-old premenopausal woman with a 14×11 mm tumor in upper outer quadrant of the left breast, diagnosed as a fibroepithelial lesion using core needle biopsy. Resection was performed. Histopathologically, the resected specimen was diagnosed as a fibroadenoma with lobular carcinoma in situ(LCIS). Tamoxifen was administered as endocrine therapy to reduce recurrence risk. We report a case of LCIS accidentally discovered by surgical resection of a benign tumor.