Association of Secondary Primary Malignancies in Cutaneous Lymphoma: A Narrative Review.

Cutaneous lymphomas are a heterogeneous group of extranodal non-Hodgkin lymphomas with distinct clinical and biological features, broadly classified into cutaneous T-cell lymphomas (CTCL) and cutaneous B-cell lymphomas (CBCL). With improved survival due to early detection and therapeutic advances, the emergence of second primary malignancies (SPMs) has become a clinical concern. SPMs, defined as new, distinct malignant neoplasms arising synchronously or metachronously with the index cancer, can significantly impair prognosis and quality of life. In this narrative review, we meticulously examine the current literature, to synthesize evidence on SPMs' incidence and risk factors in patients with primary cutaneous lymphomas. Evidence from population-based and institutional studies consistently demonstrates elevated risks of hematologic and solid tumors in CTCL. By contrast, data on CBCL remain limited, though recent population-based analyses suggest increased risks of certain hematologic malignancies and solid tumors. We further propose development mechanisms for SPMs, including treatment-related mutagenesis, shared genetic susceptibilities, chronic antigenic stimulation, and immune dysregulation. Lastly, we highlight the clinical implications of these findings, underscoring the need for vigilant surveillance, patient education, and tailored screening strategies. Future research should prioritize large-scale, prospective, and molecularly integrated studies to refine risk stratification and guide personalized survivorship care of this vulnerable population.