Whether they are mammographically visible or not, breast ultrasonography is widely used for differential diagnosis of palpable breast masses. The aim of this study is to evaluate the usefulness of cytological examinations and ultrasonographical follow-ups in the management of non-palpable, mammographically non-visible breast masses incidentally detected only by ultrasonography screening.

One hundred forty-six lesions of non-palpable and mammographically non-visible, but ultrasonographically detected solid masses (sonic masses) from 120 female patients were examined at the Breast Clinic, Chungbuk National University Hospital from January, 2000, to February, 2003. We performed ultrasonogram-guided percutaneous fine-needle aspiration biopsy in all sonic masses and proceeded all sonic masses by sequential ultrasonography at 3-, 6- and 12-month intervals if there was no suspicion of malignancy.

One hundred thirty-eight lesions (94.5%) were ultrasonographically diagnosed as benign and eight lesions (5.5%) as malignant. Eight ultrasonographically malignant lesions were all proved to be benign by cytological examinations or ultrasonogram-guided needle localization biopsies and not palpable during the follow-up period. Cytological interpretations revealed 127 lesions (87.0%) as benign, 5 lesions (3.4%) as atypical epithelial cells and 14 lesions (9.6%) as nondiagnostic. Five atypical epithelial lesions were found benign through ultrasonogram-guided needle localization biopsies or core needle biopsies in the final diagnosis. The ultrasonography was used for follow-up in all lesions. There was no evidence of malignancy in any lesion during the follow-up.

In our study, there was no evidence of malignancy in breast sonic masses during the follow-up period. Our data showed that sequential ultrasonographical follow-up is sufficient for ultrasonographically benign sonic masses.