The study evaluated the protein expression levels of FK506-binding protein 12 (FKBP12) in hepatocellular carcinoma (HCC) and paracancerous tissues using immunohistochemistry (IHC). This study aimed to determine the role of FKBP12 in the outcome of liver transplantation recipients with HCC, especially those exceeding the Milan criteria. In addition, we explored how sirolimus administration affected LT recipients'prognosis depending on different FKBP12 expression, aiming to provide some advice for clinical sirolimus application after LT.

Inclusion Criteria:

• (1) pathologically confirmed HCC (2) full post-LT follow-up record

Exclusion Criteria:

• (1)sirolimus treatment less than 30 days or after tumor recurrence (2)died within 90 days (3)underwent multiple-organ transplantation

Deceased donor LT surgery was performed in all recipients at our center between January 1, 2015 and January 1, 2021. China Liver Transplant Registry database (http://www.cltr.org) was used to obtain clinical information about patients, which included age, gender, pathological characteristics, pre-LT alpha-fetoprotein (AFP), loco-regional therapy (including transcatheter arterial chemoembolization (TACE) and radiofrequency ablation (RFA)) before LT, model for end-stage liver disease (MELD) score, Child-Pugh score, hepatitis B virus status, sirolimus administration, date of surgery, recurrence, last follow up, and death. LT recipients were required for a follow-up examination every 3 months.