Abstract

Introduction: Diffuse Large B-cell Lymphoma (DLBCL) with positive T-cell clonality is exceptionally rare. Although extranodal DLBCL can involve skin, it is rare to find heavy admixed T-cell infiltrate, and its prognostic and therapeutic implication remains elusive.

Case Presentation: A 77-year-old male with a 5-year history of supraglottic DLBCL and IgM MGUS presented with a right leg lesion. The PET scan revealed multifocal cutaneous and subcutaneous uptake along the right lower extremity. A punch biopsy demonstrated dense dermal atypical lymphoid infiltrate with diffuse monotonous sheets of large cells. Numerous mitotic figures were present. Atypical cells showed diffuse immunopositivity for CD20, MUM1, FOXP1 and negative staining for EBER, CD34, P63, CD30, SOX10, and CD10. Ki67 revealed a high proliferation rate. CD3 highlighted numerous admixed T-cells. BCL6 and BCL2 were patchy whereas MYC immunostain was positive. Molecular studies showed clonal TRG and TRB gene rearrangements as well as clonal IGH and IGK gene rearrangements.

The differential diagnosis included DLBCL, leg type, systemic DLBCL involving the skin, and primary cutaneous follicle center lymphoma with diffuse large cells.

Discussion: The identification of heavy T-cell infiltrates in DLBCL along with clonal TRG and TRB gene rearrangements is very unusual. These tumor-infiltrating T-cells may have a role in the development and progression of lymphoma and may have implications for treatment response and prognosis.