Update on the Diagnosis and Treatment of Combined Hepatocellular Cholangiocarcinoma

Combined hepatocellular-cholangiocarcinoma (cHCC-CCA) is a unique type of liver tumor that contains both hepatocellular carcinoma and cholangiocarcinoma components within a single tumor. The fifth edition of the World Health Organization classification provides a definition and diagnostic criteria for cHCC-CCA. However, the heterogeneous histomorphology and presentation resulting from variation of the proportion of each component poses challenges for clinical diagnosis and treatment. A diagnosis of cHCC-CCA may be suggested by the synchronous elevation of serum tumor markers for hepatocellular carcinoma and cholangiocarcinoma, a mixed enhancement pattern on imaging, and a discrepancy between the elevation of tumor marker and the imaging enhancement pattern. Histopathological examination using hematoxylin and eosin staining is considered the gold standard for diagnosing cHCC-CCA, and comprehensive examination of resection or biopsy specimens is crucial for an accurate diagnosis. Currently, there is no standard treatment for cHCC-CCA, and surgery is the mainstay. Anatomic hepatectomy with lymphadenectomy is among the recommended surgical procedures. The role of liver transplantation in the management of cHCC-CCA is still uncertain. Transarterial chemoembolization may be effective for unresectable cHCC-CCA, particularly for hypervascular tumors. However, the available evidence does not support systemic therapy for advanced cHCC-CCA. The prognosis of cHCC-CCA is generally poor, and there is no established staging system. Further research is needed to better understand the histogenesis and clinical management of cHCC-CCA. This review provides an overview of the current literature on cHCC-CCA with a focus on its clinical characteristics, pathological diagnosis, and management.