Unexpected discovery of intrahepatic cholangiocarcinoma during follow-up in two cases of liver cysts: case report.

Background: The liver cyst is commonly treated by hepatobiliary surgery. Generally, most patients show no apparent symptoms and often get diagnosed accidentally during the imaging examinations. In addition, most patients with liver cysts follow a benign course, with fewer severe complications and rare occurrences of malignant changes. Therefore, based on disease characteristics and healthcare costs, long-term regular follow-up of liver cysts are rarely performed clinically. Case Description: Here, we reported two previously treated or observed cases for liver cysts, where intrahepatic neoplastic lesions were found unexpectedly at the liver cyst during follow-up. These two patients' clinical manifestations and laboratory examinations lacked specificity with unclear pre-operative diagnosis, whereas the post-operative pathology confirmed cholangiocarcinoma. One of the patients was a 64-year-old female with right upper abdominal distension. She underwent cyst fenestration for a liver cyst 3 years ago. In the latest admission, imaging examination revealed a tumor in the left inner lobe of the liver. The tumor was located in the exact fenestration location, and the pathological diagnosis of cholangiocarcinoma was made after surgical resection. The patient received Lenvatinib post-operatively and had no recurrence during the follow-up. Another patient, a 68-year-old woman, was asymptomatic, but the liver margin was palpable under the ribs on her physical examination. She had a previous diagnosis of liver cysts and was on regular yearly follow-up. In the last follow-up, a tumor was found close to a cyst. It was diagnosed as intrahepatic cystadenocarcinoma before surgery; however, the pathological features after surgical resection were more consistent with the cholangiocarcinoma. The patient had lung metastases 2 months after the surgery, but her condition improved after receiving targeted therapy and immunotherapy. Moreover, she is alive to this day. Conclusions: We reported 2 cases of intrahepatic cholangiocarcinoma discovered accidentally during the follow-up of hepatic cysts. The location of the malignant tumor coincided with the location of the cyst, making the clinical differential diagnosis problematic. Therefore, it is necessary to be vigilant about the possibility of combined malignant tumors for the follow-up of complex cysts, as early detection and treatment may help improve the prognosis of these patients. After surgery, multimodal therapy, including chemotherapy, immunotherapy, and targeted therapy, is helpful.