Introduction
Liver transplantation is the most effective treatment for end-stage liver disease in children. Due to the use of immunosuppressants, infection by the Epstein–Barr virus (EBV) is common after pediatric liver transplantation (pLT)(1), and post-transplant lymphoproliferative disease (PTLD) related to EBV is a serious complication with a poor prognosis that can lead to death after pLT(2, 3).
Compared to adults, children with PTLD show obvious characteristics in terms of incidence rate and performance. The incidence of PTLD after solid organ transplantation in children is higher than that in adults(4). With the growing number of pLT procedures in recent years, the number of pediatric cases of EBV-related PTLD has also increased year by year. Different from the 80%–90% rate of EBV infection in adults, only about 20%–50% of children are EBV carriers by the age of 5 years, and their symptoms may be hidden or they may show symptoms of EBV infection (fever, night sweats, and weight loss), lymph node hyperplasia, or graft dysfunction(5-8).
Histopathological examination is the gold standard for the diagnosis and classification of PTLD after pLT. According to the World Health Organization classification of lymphomas (2017) revised edition, PTLD can be divided into the following categories: (I) non-destructive PTLD, including plasmacytic hyperplasia PTLD, infectious mononucleosis PTLD, and florid follicular hyperplasia PTLD; (II) polymorphic PTLD; (III) monomorphic PTLD, including B- and T-/natural killer cell types; and (IV) classical Hodgkin’s lymphoma PTLD(9-11). However, as an invasive assessment, histopathological examination will inevitably do some harm to patients. As a non-invasive method,18F-fluoro-2-deoxy-D-glucose (18F-FDG) positron emission tomography (PET)/computed tomography (CT) imaging has been widely used in adult PTLD, but its application in children is less commonly reported. A recent study involving 28 children with PTLD showed that 18F-FDG PET/CT has a good positive predictive value (PPV) and specificity, but its sensitivity and negative predictive value (NPV) were poor. This may be because children grow and develop rapidly, and there are high metabolic regions such as the brain, kidneys, and heart that render18F-FDG PET/CT unable to detect PTLD that can be confirmed by histology in these regions(12). Studies have shown that the median peak standardized uptake value (SUVpeak) at the biopsy site of monomorphic PTLD is significantly higher than those of the polymorphic and non-destructive subtypes of PTLD. However, it is difficult to distinguish between PTLD-negative cases and non-destructive PTLD cases using SUVpeak due to the significant SUV overlap of the different subtypes(13). Therefore, it is of significant interest to find an index that can distinguish PTLD-negative cases and non-destructive PTLD cases with high sensitivity, specificity, PPV, NPV, and accuracy; confirm or refute the clinical suspicion of PTLD; and identify suggestive lesions accessible for biopsy. This study reviewed and collected clinical and pathological data of pLT patients who underwent18F-FDG PET/CT and lymph node biopsy, explored the indicators that can effectively distinguish PTLD-negative cases and non-destructive PTLD cases, and evaluated their effects.