Introduction: Diffuse large B-cell Lymphoma (DLBCL) is a heterogeneous group of malignant tumors with diverse prognoses, histological appearances, and clinical symptoms. While it commonly affects lymphoid tissues, its occurrence in the nasal cavity and paranasal sinuses is rare and poses significant diagnostic challenges. Case presentation: We present a case of a 53-year-old man with a history of testicular non-Hodgkin lymphoma treated five months prior. He presented with symptoms initially misdiagnosed as a dental abscess, which was later identified as DLBCL in the maxillary sinus. Discussion: The etiology of primary lymphoma in the oral region remains unclear. Due to its rarity, specific prognostic factors and optimal treatment strategies are not well-established. This case highlights the diagnostic challenges and underscores the importance of considering lymphoma in the differential diagnosis of non-responsive dental abscesses. Conclusion: This case underscores the importance of thorough investigation in patients with non-responsive dental abscesses. Early identification and appropriate management of DLBCL in uncommon sites require heightened clinical awareness and interdisciplinary collaboration. The optimal treatment approach remains debated and warrants further research.