Pathogenicity of pediatric thymic lymphoepithelioma- like carcinoma with Epstein-Barr virus infection and its treatment with immunotherapy

Background: Thymic lymphoepithelioma-like carcinoma (LELC) is an extremely rare neoplasm in children. The causative role of Epstein-Barr virus (EBV) in the pediatric thymic LELC is unclear with limited treatment guidelines. Materials and methods: At our hospital, a 17-year old boy with thymic LELC was studied based on plasma levels of EBV DNA measured multiple times using real time quantitative polymerase chain reaction (RT-QPCR). For comparison, other patients <18 years old with thymic LELC reported in the English literature were also reviewed. Results: There were only 17 cases of pediatric thymic LELC in the literature. Including the present case, we analyzed a total of 18 such patients. The male to female ratio was 14:4, and the average age was 12.6 years old (range: 4 to 17). Of these 18 patients, the associations with EBV were not determined in 6 due to incomplete data, and the remaining 12 were all EBV-related. The mortality rate of pediatric thymic LELC was 68.8%, with an average survival time of 12.6 months after diagnosis. The plasma level of EBV RT-QPCR of the patient was 77048 copies/ml before chemotherapy. As his expression of PD-L1/PD-1 was 70%, pembrolizumab (2 mg/kg for one day) was also given. After 6 cycles of the above treatments, his CT scan showed a reduction in tumor size of >50% at the mediastinum. Conclusion: Despite limited data and our single case, we are inclined to conclude that children with thymic LELC likely associate with EBV pathogenicity. Immunotherapy may be useful in improving the prognosis.