## Hypertrophic Scar vs. Keloid: Clinical Discrimination ### Case Context The patient has a post-surgical scar (8 weeks post-op) with excessive fibrosis confined to the incision line. This clinical presentation is classic for a hypertrophic scar, not a keloid. ### Boundary as the Primary Discriminator **Key Point:** The spatial confinement of the scar tissue to the original wound margin is the single best clinical feature that distinguishes hypertrophic scars from keloids. ### Comparative Table | Criterion | Hypertrophic Scar | Keloid | |-----------|-------------------|--------| | **Boundary Behavior** | Stays within original wound margin | Breaches and extends beyond original margin | | **Clinical Presentation** | Raised, firm, confined scar | Raised, firm, extends into normal skin | | **Post-op Timeline** | Typically 4–12 weeks | Can appear weeks to years later | | **Spontaneous Regression** | Common (1–2 years) | Rare; persists indefinitely | | **Ethnic Predisposition** | Minimal | Increased in darker skin phenotypes | | **Recurrence After Excision** | ~5–15% | ~45–50% | ### Why Boundary Matters **High-Yield:** The breach of the original wound boundary indicates autonomous, pathologic fibroblast proliferation that is characteristic of keloid formation. Confinement within the boundary suggests a self-limited, exaggerated but ultimately normal wound-healing response (hypertrophic scar). ### Clinical Pearl In the operating room or clinic, the simplest question to ask: "Does the raised scar tissue stay within the scar line, or does it spill into normal skin?" If confined → hypertrophic; if spilling → keloid. This distinction drives management: hypertrophic scars often improve with time and conservative measures (pressure garments, silicone), whereas keloids require more aggressive intervention (intralesional steroids, radiation, surgical excision with adjuvant therapy). ### Mnemonic **"SCAR STAYS IN ITS LANE" = Hypertrophic** **"SCAR INVADES NEXT LANE" = Keloid**
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