Track

Abstract

Primary cutaneous peripheral T-cell lymphomas with a T-follicular helper phenotype (pcTFH-PTCL) pose significant diagnostic challenges due to their overlapping clinical and histological features with other lymphoproliferative disorders, poor characterization and ambiguous categorization within the current WHO classification scheme of hematolymphoid neoplasms.  Here, we present a case of a 60-year-old male with a 12-year history of primary cutaneous lymphoma, initially diagnosed as peripheral T-cell lymphoma, NOS, later thought to represent mycosis fungoides with large cell transformation recalcitrant to multimodal therapy, prompting stem cell transplant with subsequent clinical remission. Three years later, he developed persistent pink poikilodermatous patches and new multifocal erythematous papules without B-symptoms, raising concern for cutaneous recurrence. Histologic examination revealed dense perivascular, perifollicular, and nodular lymphocytic infiltrates of small to medium-sized lymphocytes with hyperchromatic and hyperconvoluted nuclei. Immunohistochemistry showed CD3+ T-cells intermixed with CD20+ B-cells in nodular configuration, with T-cells exhibiting an elevated CD4:CD8 ratio, preserved CD5, weak CD2, diminished CD7 and high PD-1 expression. Molecular testing confirmed clonal TCR amplification and negative B-cell clonality, consistent with recurrent cutaneous lymphoma with a follicular helper T-cell phenotype. Comprehensive staging including PET/CT and blood analysis did not identify any visceral involvement or aberrant T- or B-cell populations. High-throughput sequencing identified matching sequences in histologic samples from initial diagnosis and this disease recurrence. No further disease progression or extracutaneous extension has been noted over 2-years on bexarotene, interferon-alpha and topical steroids. This case highlights the diagnostic complexity of pcTFH-PTCL and underscores the need for refined classification to improve its recognition and management.