Supplementary Material for: Metastatic EBV-associated lymphoepithelioma-like carcinoma of small bowel origin

Introduction: Lymphoepithelioma-like carcinomas (LELC) are rare tumors composed of poorly differentiated epithelial cells with a prominent lymphoid stromal infiltrate. This tumor histology has been described in various tissues of origin including the nasopharynx, lung, thymus, breast, bladder, and others. However, involvement of the gastrointestinal system is relatively uncommon and has most often been described in the stomach. Case Presentation: Here we report a case of a young woman who presented with metastatic disease of unclear primary involving the liver and abdominal lymph nodes, along with marked EBV viremia. She was ultimately found to have metastatic EBV-associated lymphoepithelioma-like carcinoma of likely small bowel origin, an uncommon tissue of origin for a rare histopathology. She was treated with chemotherapy and immunotherapy regimens commonly used for gastrointestinal and biliary cancers, with an initial treatment response but ultimately rapid tumor progression. Conclusion: LELCs are rare tumors that uncommonly involve the gastrointestinal system, particularly the small bowel. Further reports are needed to better understand disease presentation, pathophysiology, prognosis, and management.