The purpose: To investigate the diagnostic accuracy of 18F-FLT PET for the suspicious lesions on mammograms and ultrasound.

1. To investigate the diagnostic accuracy of 18F-FLT PET for the suspicious lesions on mammograms and ultrasound, using the pathologic result of biopsy as gold standard, and to determine whether 18F-FLT PET can increase the specificity in breast lesion diagnosis and thus reduce the unnecessary biopsy.
2. To evaluate whether 18F-FLT PET is a cost-effective imaging modality for breast cancer diagnosis.

Inclusion Criteria:

1. Women aged between 20 to 80 years
2. women who have localized findings on mammography and / or ultrasound and will receive biopsy.
3. The lesions on the conventional imaging measure >=1cm
4. WBC count >=3000/L, or platelet>=75,000/L
5. Liver function, AST or ALT < 78 U/L
6. Renal function, Creatinine < 2.0 mg/dl.The laboratory examinations should be performed within 4months before our study.

Exclusion Criteria:

1. Pregnant women or who are planning to be pregnant.
2. Known cancers in other organs.
3. Women who are not able to cooperate with the PET/CT examination.