We wanted to evaluate the characteristics of those lesions showing insufficient results on ultrasound-guided core needle biopsy.

We retrospectively reviewed the pathologic results of 131 lesions from patients who underwent ultrasound-guided core needle biopsy following Mammotome or surgical excisional biopsy from January 2004 to December 2004.

Compared with excisional biopsy, ultrasound-guided core needle biopsy showed 14 lesions with discordant results and 9 lesions with indeterminate results. 5 lesions were overestimated and 9 lesions were underestimated on the core needle biopsies. According to the histological tumor types, the papillary tumors showed 66.6% discordance or indetermination, and the phyllodes tumors showed 50% discordance or indetermination.

On the results of core needle biopsy, discordant or indeterminate results were frequently reported for papillary and phyllodes tumor. Therefore, excisional biopsy is recommended for these types of tumor.