Track: Case Reports

Abstract:

Follicular helper T-cell lymphoma (International Consensus Classification)—also termed nodal T follicular helper (TFH) cell lymphoma (WHO 5^th edition)—is an aggressive neoplasm of mature follicular helper T-cells. While it primarily involves lymph nodes, secondary cutaneous involvement is not uncommon. We describe a 70-year-old woman presenting with multiple erythematous patches that progressed to widespread, well-circumscribed, nodular lesions over a year. Imaging revealed numerous fluorodeoxyglucose-avid cutaneous and subcutaneous lesions, without pathologic lymphadenopathy. Multiple skin punch biopsies, including of a shoulder lesion, were performed. Histopathologic examination revealed a diffuse dermal infiltrate of large, atypical lymphocytes with eosinophilic cytoplasm, irregular nuclei, vesicular chromatin, small nucleoli, prominent apoptosis, and focal angiocentricity. Immunohistochemistry demonstrated a CD3-positive T-cell population coexpressing CD2, CD4, TCR-βF1, multiple TFH markers including CD279, BCL6, CXCL13, and ICOS, with weak CD5 and CD7 expression and negativity for CD8, CD25, CD56, IDH2-R172K, TRBC1, and TCR-delta. A CD20-positive B-cell population staining positive for Epstein-Barr virus (EBV) encoded RNA in situ hybridization was also identified. Molecular studies revealed clonal T-cell and immunoglobulin gene rearrangements. Next generation sequencing detected DNMT3A, RHOA, and TET2 mutations in the skin. Peripheral blood flow cytometry also revealed a clonal CD4-positive T-cell population. Overall, the findings support a diagnosis of T-cell lymphoma with TFH phenotype and associated EBV-positive clonal B-cell proliferation. The patient has begun treatment with brentuximab vedotin plus CHP (cyclophosphamide, doxorubicin, prednisone) and is responding well. This case is unusual for its predominantly cutaneous presentation without apparent nodal disease, highlighting the importance of dermatopathologic assessment and clinicopathologic correlation.

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Rebecca King