Sonographic differentiation of benign and malignant cystic lesions of the breast.

OBJECTIVE: The purpose of this study was to subdivide the types of sonographic findings of benign versus malignant cystic masses and to determine appropriate patient care according to the sonographic findings with pathologic correlation. METHODS: The sonographic findings of 175 symptomatic cystic breast lesions were pathologically proven and reviewed retrospectively. Cystic lesions were classified as 6 types: simple cysts (type I), clustered cysts (type II), cysts with thin septa (type III), complicated cysts (type IV), cystic masses with a thick wall/septa or nodules (type V), and complex solid and cystic masses (type VI). Sonographic findings were compared with the pathologic results and were evaluated according to the incidence of benign and malignant masses. RESULTS: All 23 type I, 15 type II, 22 type III, and 35 type IV cases were pathologically proven to be benign. Seven (25.9%) of the 27 type V cases and 33 (62.3%) of the 53 type VI cases were proven to be malignant. We analyzed the shapes and margins of 80 cases of cystic masses with a solid component (types V and VI); 16 (44%) of 36 sonographically circumscribed masses were malignant. CONCLUSIONS: Because the sonographically detected simple cysts (type I), clustered cysts (type II), and cysts with thin septa (type III) were all benign, annual routine follow-up appears reasonable. Symptomatic complicated cysts (type IV) should be aspirated and appropriately treated according to clinical symptoms. Cystic masses with a solid component (types V and VI) should be examined by biopsy with pathologic confirmation.