Recurrent undifferentiated embryonal sarcoma of the liver in adult patient treated by pembrolizumab: A case report

BACKGROUND: Undifferentiated embryonal sarcoma of the liver (UESL) is a neoplasm that rarely develops in adults. The main treatments for UESL are upfront gross total surgical resection and adjuvant multiagent chemotherapy. Here, we report a case of recurrent UESL in an adult treated with pembrolizumab and discuss a method to identify proper candidates for antibody of programmed cell death protein 1 (anti-PD-1) treatment. CASE SUMMARY: A 69-year-old woman was admitted for abdominal pain that developed for 1 wk. Computed tomography showed a 16 cm mass in the right lobe of the liver. Right hemihepatectomy and lymphadenectomy were performed, and histological diagnosis was UESL. Six months later, the patient suffered from painless obstructive jaundice, and positron emission tomography-computed tomography revealed multiple metastases. Then, percutaneous transhepatic cholangial drainage was applied to reduce jaundice, and radiofrequency ablation was used to control the lesion near the hepatic hilum. However, the patient suffered from a serious fever caused by the tumor. The patient received treatment with pembrolizumab, and the prescribed dosage was 2 mg/kg every 3 wk. After the seventh dose, positron emission tomography-computed tomography revealed that the multiple metastases had nearly disappeared. Radiologic exam was used to evaluate the disease state, and no new lesions were found. Next-generation sequencing and immunohistology were applied to determine the reason why the patient had such a favorable response to pembrolizumab. Tumor mutation burden, microsatellite instability, and programmed death ligand 1 expression can be combined to predict the effect of PD-1 antibodies. When every one of these biomarkers are detected in a tumor patient, the patient may be a proper candidate for PD-1 antibodies. CONCLUSION: Anti-PD-1 treatment for tumors needs further research to identify indications and proper biomarkers.