Abstract

Objective: To describe and compare the histopathological characteristics of keloids and hypertrophic scars in Vietnamese adults. Materials and Methods: This prospective cross-sectional study was conducted on scar specimens obtained from 15 patients at Le Huu Trac National Burn Hospital from October 2025 to May 2026. Histopathological changes were observed and evaluated on hematoxylin and eosin (H&E)-stained sections under light microscopy. Comparisons were performed between keloids and hypertrophic scars, as well as between the central and peripheral regions of the scars. Results: The concordance between clinical and histopathological diagnoses was 93.3% with κ = 0.857. Both keloids and hypertrophic scars demonstrated increased epidermal thickness, alteration, and flattening of the rete ridges. Keloids showed a higher density of inflammatory cells than hypertrophic scars in both the central and peripheral regions (p < 0.01), with inflammatory reactions being more prominent in the peripheral region. Keloidal collagen was observed in 77.78% of keloid cases and was absent in hypertrophic scars (p = 0.007); in several cases, keloidal collagen was identified only in the peripheral region. Blood vessels oriented perpendicular to the skin surface tended to be more common in hypertrophic scars (83.33%). Keloids demonstrated marked histopathological heterogeneity both among different specimens and between regions within the same specimen. Conclusion: Keloids and hypertrophic scars exhibit several distinct histopathological characteristics; however, substantial overlap remains on routine histopathological examination. Additional histological markers and advanced analytical methods are needed to improve the diagnostic differentiation between keloids and hypertrophic scars.