Angioimmunoblastic T-cell lymphoma of the oral cavity presenting as gingival mass: report of the histopathologic and molecular characteristics of an unusual case featuring clonal T-cell receptor γ gene rearrangement by polymerase chain reaction.

Angioimmunoblastic T-cell lymphoma (AITL) is a rare neoplastic process constituting 15% to 20% of peripheral T-cell lymphomas. We report the clinicopathologic and molecular characteristics of an unusual intraoral manifestation of AITL. A 35-year-old white man with a history of AITL presented with a 2.5-cm, poorly circumscribed, erythematous, exophytic lesion occupying the free and attached buccal gingiva of the right maxillary lateral incisor and canine. Histopathologically, the tumor showed diffuse and intense polymorphic infiltration by small to medium-sized lymphocytes admixed with numerous eosinophils. The neoplastic cells showed strong and diffuse reactivity for CD2, CD3, CD4, CD10, and PD-1 (programmed cell death 1 [PDCD1]). Rare immunopositivity was seen with BCL6 (B-cell CLL/lymphoma 6) and CXCL13 (chemokine [C-X-C motif] ligand 13). Neoplastic cells were negative for CD7 and EBER ISH (Epstein-Barr virus-encoded small RNA in situ hybridization). CD21 did not show any increased follicular dendritic cell component. Polymerase chain reaction-based assay found monoclonal T-cell receptor γ (TRG) gene rearrangements. Diagnosis of recurrent/residual AITL was rendered. Chemotherapy was administered, with the intraoral tumor resolving completely 3 months later.