Dermatologic Perspectives on Primary Cutaneous Lymphomas: Clinicopathologic Spectrum, Molecular Insights and Evolving Treatment Paradigms

Primary cutaneous lymphomas (PCLs) are a heterogeneous group of extranodal non-Hodgkin lymphomas presenting in the skin without evidence of extracutaneous disease at diagnosis. They encompass a broad clinicopathologic spectrum dominated by cutaneous T-cell lymphomas (CTCL), primarily mycosis fungoides (MF) and Sézary syndrome (SS), and by distinct entities of primary cutaneous B-cell lymphomas (PCBCL). Recent updates of the WHO–EORTC classification have refined disease definitions and introduced new entities and lymphoproliferative disorders, with direct consequences for prognosis and therapeutic decision-making. Parallel advances in genomics and im-munobiology have revealed recurrent alterations in T-cell receptor (TCR) signalling, JAK–STAT and NF-κB pathways, as well as hallmarks of immune evasion in the tumour microenvironment, providing a rationale for targeted and immune-based therapies. This narrative review, written from a dermatologic perspective, summarises current concepts in the classification, epidemiology and clinicopathologic features of the major PCL subtypes. We discuss key molecular drivers of CTCL and PCBCL, practical aspects of diagnosis and staging at the interface between dermatology, pathology and haematology, and the role of non-invasive imaging. We then review the contemporary therapeutic armamentarium, including skin-directed therapies, systemic biologic agents and chemotherapy, and emphasise pivotal trials of antibody-drug conjugates and immune therapies such as brentuximab vedotin and mogamulizumab. Finally, we highlight unmet needs, including diagnostic delay, real-world prognostic stratification, manage-ment of advanced and relapsed disease, and the integration of biomarkers into person-alised care. Dermatologists occupy a central role in early recognition, longitudinal monitoring and multidisciplinary management of PCLs, and ongoing collaboration between specialties is essential to translate molecular insights into improved patient outcomes.