Suggestions for Redefining, Classifying, and Naming ICC

Hepatobiliary cell cancer (intrahepatic cholangiocarcinoma, ICC) is a highly malignant liver tumor with strong invasiveness and poor prognosis. ICC originates from the bile duct located in the liver, and it can be classified as both primary liver cancer and bile duct cancer, leading to unclear classification and naming controversies. The more the truth is debated, the clearer it becomes. Upholding the concept of a hundred schools of thought contending, this journal establishes an academic debate column for scholars and readers to discuss different academic opinions, hoping to deepen and clarify the issues through enthusiastic attention and rational thinking, thus promoting academic prosperity and development.

Regarding ICC, Professor Cong Wenming defines it as: “Specifically refers to malignant tumors occurring in the epithelial cells of the intrahepatic bile duct tree at all levels, including malignant tumors originating from the secondary bile ducts near the hilum of the liver, the segmental bile ducts, and their associated periductal glands (hilar-type ICC), as well as malignant tumors that grow in the peripheral parts of the liver, originating from the small bile ducts below the liver segment (interlobular bile ducts, small bile ducts) (peripheral-type ICC).” This definition has a broad scope for ICC, with tumor occurrence sites ranging from small bile ducts in the liver’s periphery to secondary bile ducts in the hilum. The closer the ICC is to the liver’s periphery, the more similar it is to hepatocellular carcinoma; the closer it is to the hilum, the more similar it is to extrahepatic bile duct cancer. ICC originating from different sites significantly differs in pathogenesis, biological behavior, histological morphology, treatment methods, and prognosis, leading to inconsistent classification and naming in clinical practice.

Both the “Consensus on the Diagnosis and Treatment of Cholangiocarcinoma” in China and the NCCN guidelines classify ICC as bile duct cancer and divide it into three subtypes: mass-forming, periductal-infiltrating, and intraductal growing. However, the “WHO Classification of Tumours of the Digestive System” (5th edition) has changed ICC to iCCA, independently staged it, and classified it as “malignant tumors of the liver and intrahepatic bile ducts”, dividing it into “small duct type iCCA” and “large duct type iCCA”, where small duct type iCCA is essentially mass-forming ICC. Whether classified into three subtypes according to the NCCN guidelines or into two pathological types according to the WHO, the differences in pathogenesis, biological behavior, histological morphology, treatment methods, and prognosis among the various subtypes are significant. See Figure 1.

In light of the above reasons, the author suggests reclassifying the original three subtypes of ICC.