37-year-old female patient who was admitted in poor general condition with altered consciousness and pleural effusion. Five months before admission, she had severe and recurrent epigastric pain, dyspepsia, weight loss and night sweats. She was diagnosed with gastritis and prescribed with relief drugsA slight improvement and the symptoms persisted. Imaging, histopathological and immunohistochemistry studies led to the diagnosis of diffuse large cell B non-Hodgkin lymphoma gastric primary germinal center phenotype. The patient was on cyclophosphamide, doxorubicin, vincristine and prednisone, plusrituximab. The evolution was favorable.