Cystic Degeneration of Hepatocellular Carcinoma Mimicking Mucinous Cystic Neoplasm.

Spontaneous regression of tumors is an extremely rare event in hepatocellular carcinoma (HCC) with only a few reports available. With the accumulation of clinical information and tumor immunogenetics, several mechanisms for the cystic changes of HCC have been suggested, including arterial thrombosis, inflammation, and rapid tumor growth. This paper reports an uncommon case of the partial regression of HCC, which was initially misdiagnosed as a mucinous cystic neoplasm of the liver due to the unusual radiologic findings. A 78-year-old female with the hepatitis B virus and liver cirrhosis presented with an approximately 5 cm-sized cystic mass of the liver. From the radiologic evidence of a papillary-like projection from the cyst wall toward the inner side, the initial impression was a mucinous cystic neoplasm of the liver. The patient underwent a surgical resection and finally, cystic degeneration of HCC, in which approximately 80% necrosis was noted. This case suggests that if a cystic neoplasm of liver appears in a patient with a high risk of HCC on a hepatobiliary imaging study, it is prudent to consider the cystic degeneration of HCC in a differential diagnosis.