RESUMEN
INTRODUCTION: Adenocarcinomas of the gastroesophageal junction (GEJ) are tumors whose incidence rates increased significantly in recent years. These tumors have a poor prognosis, and are treated with a palliative approach when diagnosed in an advanced stage. Some tumors overexpress PDL-1 proteins which are partially responsible for the "immune escape" of tumor cells. However, this over-expression enables the use of an immunotherapeutic treatment approach. Immunotherapy using anti-PD1/PDL-1 shows promising results in patients with metastatic GEJ tumors. In the present case report, we describe a young patient who was diagnosed with a non-resectable GEJ adenocarcinoma and was found to have almost 100% positivity for PDL-1 in the tumor biopsy, using standard immunohistochemistry. The patient had rapid and complete response to the anti-PD1 antibody treatment with further development of immune mediated side effects.