A case of cystadenocarcinoma of the liver

A case of cystadenocarcinoma of the liver is reported. The patient was a 73‐year‐old woman in whom a tumor was detected in the lateral segment of the liver during a health examination. Ultrasonograms and computed tomograms showed a multilocular cystic mass. Magnetic resonance imaging (MRI) showed a multilocular lowintensity mass, including a high‐intensity portion and a portal branch compressed by the tumor. MRI with gadolinium showed an enhanced cyst wall. The cystic part of the tumor became smaller and the solid part became larger over a 1‐month period, indicating that the tumor was malignant. Subsegmentectomy (S 3 ) was performed and cystadenocarcinoma with cystadenoma was diagnosed by histopathological examination. Identification of changes in the appearance of a tumor should be helpful for the differential diagnosis of cystadenoma and cystadenocarcinoma.