Primary Cutaneous CD4+ Small/Medium T-Cell Lymphoproliferative Disorder: A Case Report and Literature Review

Objective: To report the clinicopathological features, immunophenotype, molecular genetic alterations, and treatment strategies of primary cutaneous CD4+ small/medium T-cell lymphoproliferative disorder (CD4pcSM-LPD).Methods: A case analysis and literature review were conducted, integrating histopathology, immunohistochemistry (IHC), molecular testing, and follow-up data.Results: CD4pcSM-LPD exhibited indolent biological behavior with a favorable prognosis. IHC revealed diffuse strong positivity for CD3 and CD4, partial loss of CD7, scattered "starry-sky" distribution of CD8, sparse expression of follicular helper T-cell markers (PD1, BCL6) in medium-to-large cells, and focal CD30 positivity. Molecular analysis identified a monoclonal TCR-B V-J rearrangement. Treatment with methotrexate achieved complete resolution of skin lesions.Conclusion: CD4pcSM-LPD is a rare polymorphic T-cell proliferative disorder characterized by indolent behavior and excellent prognosis.Due to its rarity, clinicians and pathologists often lack familiarity with this entity, leading to misdiagnosis or overtreatment.This study highlights the clinicopathological, immunophenotypic, and molecular features of CD4pcSM-LPD, emphasizing its distinct diagnostic criteria and management strategies.