A 42-yeаr-оld wоmаn undergоes а routine abdominal ultrasound for mild, intermittent right upper quadrant discomfort. The sonographer notes a well-defined, uniformly bright (hyperechoic), 4.5 cm mass in the right lobe of the liver. When evaluating the mass with color Doppler, there is an absence of internal blood flow (no flow). Her liver enzyme blood tests are completely normal. What is the most likely diagnosis?