Mucinous lesions in the breast are uncommon. They constitute a wide spectrum of lesions ranging from extravasated mucin associated with fibrocystic change to mucinous carcinoma. There are limited data on the reliability of core biopsy in the diagnosis of mucinous lesions of the breast. We reviewed the core biopsy and surgical biopsy diagnoses in 32 mucinous lesions of the breast. We conclude that core biopsy is highly reliable for accurate diagnosis of mucinous lesions of the breast.