Case 10 Answer

This is at least a complex cyst or mixed solid and cystic mass. There are multiple echoes at one end of the mass which were not artifactual. It is important not to overlook the solid-appearing portions of any cyst one is evaluating. [RSNA EJ 1999;3 Online.]

This patient underwent ultrasound-guided cyst aspiration which yielded yellowish fluid. Cytology was benign. The lump recurred soon after aspiration. Follow-up ultrasound examination showed the following:

























What is the most likely diagnosis?