Thermal ablation has been recommended by worldwide guidelines as first-line treatment for hepatocellular carcinoma (HCC), while evidence regarding its efficacy for primary intrahepatic cholangiocarcinoma (iCCA) is lacking. The goal of this observational study is to study the efficacy of ablation in treating iCCA by comparing its prognosis with surgery. The main questions it aims to answer are:

• Whether microwave ablation could achieve similar efficacy with liver resection in treating iCCA
• What is the risk factor for ablation or surgery in treating iCCA
• What kind of iCCA patients could receive ablation as their first-line treatment In this real-world multicenter cohort study, we will collect data of iCCA patients from hospitals who underwent microwave ablation (MWA) or liver resection (LR) for tumors within Milan criteria. Survival will be compared between patients treated by MWA or LR.

Inclusion Criteria:

1. pathologically diagnosed iCCA based on the WHO classifications;
2. curative-intent liver resection or microwave ablation;
3. tumor within Milan criteria, namely single tumor ≤5cm in maximum diameter; multiple tumors ≤3 in number and each ≤3cm; no evidence of major vascular/hilar invasion, extrahepatic/lymphatic metastasis or other malignancies;
4. age ≥18 years.

Exclusion Criteria:

Patients not meeting any one of the inclusion criteria were excluded.

Chinese patients pathologically diagnosed with intrahepatic cholangiocarcinoma