Mechanistic Insights into Secondary Lymphedema: The Role of Inflammatory Cytokines and Fibrotic Pathways in Post-Surgical Patients.

BACKGROUND: Secondary lymphedema is a debilitating complication following oncologic surgery, characterized by progressive tissue fibrosis and chronic inflammation. Although transforming growth factor-beta 1 (TGF-β1) has been established as a central mediator of fibrotic remodeling, the broader interplay between pro-inflammatory cytokines and downstream fibrotic signaling cascades in post-surgical lymphedematous tissue remains poorly understood. METHODS: Skin and subcutaneous tissue biopsies were prospectively collected from 126 patients with unilateral breast cancer-related lymphedema and 58 matched controls across three tertiary centers between January 2024 and December 2025. Tissue specimens were analyzed using immunohistochemistry, quantitative real-time PCR, multiplex cytokine profiling, and Western blotting. Correlations between cytokine expression, fibrotic markers, and clinical severity were evaluated. RESULTS: Lymphedematous tissues exhibited significantly elevated expression of TGF-β1, interleukin-6 (IL-6), interleukin-13 (IL-13), and tumor necrosis factor-alpha (TNF-α) compared with controls (all P < 0.01). Concurrent activation of Smad2/3 and STAT3 signaling pathways was observed, with both correlating positively with disease severity. Multivariate regression identified TGF-β1, IL-6, and IL-13 as independent predictors of fibrotic burden, whereas TNF-α lost significance after adjustment for confounders. Lymphatic vessel density was inversely associated with cytokine levels and fibrotic severity. CONCLUSION: Secondary upper extremity lymphedema following breast cancer surgery is driven by a coordinated inflammatory and fibrotic axis involving TGF-β1, IL-6, and IL-13 through convergent Smad2/3 and STAT3 signaling. These findings support the development of multi-pathway therapeutic strategies beyond single-agent anti-fibrotic approaches for post-surgical lymphedema.