DOI: https://doi.org/10.36347/sjmcr.2026.v14i07.024

Pages: 1713-1717

Background: Diffuse large B-cell lymphoma (DLBCL) is the most common subtype of non-Hodgkin lymphoma (NHL) in adults. Primary gingival involvement is exceptional and constitutes a major diagnostic pitfall, particularly when associated with mandibular bone lysis and ipsilateral cervical lymphadenopathy, a presentation that closely mimics oral squamous cell carcinoma. Case presentation: We report the case of a 61-year-old man with no notable medical history who presented with a 3-month history of a right lower vestibular gingival swelling. Facial MRI showed an expansile process of the right lower vestibular gingiva lysing the horizontal ramus of the right hemimandible, with an ipsilateral cervical lymph node larger than 3 cm, initially staged T4a N2a Mx according to the TNM classification used for upper aerodigestive tract carcinomas. Gingival biopsy redirected the diagnosis toward a non-germinal center DLBCL: tumour cells showed intense, diffuse expression of CD20, moderate expression of P53 (40%), and a very high Ki-67 proliferation index (95%), and were negative for CD3, CD5, CD10, BCL2, BCL6, CD30 and TdT. The patient was referred to the haematology department for completion of staging work-up and specialised treatment. Discussion: This case highlights the clinical and radiological difficulty in distinguishing gingivo-mandibular squamous cell carcinoma from primary gingival lymphoma, and underlines the importance of systematic biopsy for any persistent, atypical gingival swelling. It also stresses the need, once the diagnosis of lymphoma is confirmed, to re-stage the disease according to the Lugano classification rather than the TNM system, which is designed for epithelial tumours. Conclusion: Early biopsy remains the cornerstone of the diagnostic work-up for atypical adult gingival masses, avoiding diagnostic delay and inappropriate management.