Keloid vs. Hypertrophic Scars: Understanding the Key Differences

# Keloid vs. Hypertrophic Scars: Understanding the Key Differences

Distinguishing Between Two Types of Raised Scars

When the skin heals after an injury, it often forms a scar. While most scars flatten and fade over time, some can become raised and prominent. Among these, keloid scars and hypertrophic scars are two distinct types that are often confused due to their similar appearance. However, understanding the key differences between them is crucial for accurate diagnosis, appropriate treatment, and effective management. Both are characterized by an overgrowth of fibrous tissue, but their growth patterns, underlying biology, and response to treatment vary significantly [1].

Key Differentiating Characteristics

The most critical distinction between keloid and hypertrophic scars lies in their growth behavior and boundaries:

* Growth Beyond Injury Site: The defining characteristic of a keloid scar is its ability to grow beyond the original boundaries of the wound. It invades the surrounding healthy skin, forming a larger, often irregularly shaped mass. In contrast, a hypertrophic scar remains confined to the site of the original injury. It may be raised and thick, but it does not spread into adjacent healthy tissue [2, 3].

* Timing of Appearance and Progression: Hypertrophic scars typically appear within weeks of the injury and may grow rapidly for a few months before stabilizing or even regressing over time. Keloids, however, can appear months or even years after the initial injury and tend to continue growing indefinitely, rarely regressing spontaneously [4].

* Appearance and Texture: Both can be red, raised, and firm. However, keloids are often described as having a shiny, rubbery, or dome-shaped appearance, and can be darker in color. Hypertrophic scars tend to be redder and more linear, following the line of the wound. Both can cause itching, pain, and tenderness.

* Histological Differences: Under a microscope, keloids show disorganized, thick, hyalinized collagen bundles that extend deep into the dermis, often with an increased number of fibroblasts and blood vessels. Hypertrophic scars, while also having increased collagen, typically show more organized, parallel collagen fibers that are confined to the original wound area [5].

* Recurrence Rate: Surgical removal of a hypertrophic scar often leads to a good outcome with a lower chance of recurrence. However, surgical excision of a keloid carries a very high risk of recurrence, often resulting in a larger keloid, unless combined with aggressive adjuvant therapies like radiation or corticosteroid injections [6].

Factors Influencing Formation

Both types of scars can result from various skin injuries, including surgical incisions, burns, trauma, acne, and piercings. However, certain factors are more strongly associated with one type over the other:

* Tension: Hypertrophic scars are often associated with wounds under high skin tension, such as those over joints.

* Genetics and Ethnicity: Keloids have a much stronger genetic predisposition and are significantly more common in individuals with darker skin tones (African, Afro-Caribbean, Asian descent) [7]. While hypertrophic scars can occur in anyone, this ethnic disparity is less pronounced.

Treatment Approaches

Due to their differing characteristics, the treatment strategies for keloids and hypertrophic scars also vary:

* Hypertrophic Scars: Often respond well to conservative treatments such as silicone sheeting, pressure therapy, and corticosteroid injections. They may also regress spontaneously.

* Keloid Scars: Require more aggressive and often combination therapies, including intralesional corticosteroids, cryotherapy, laser therapy, and surgical excision followed by adjuvant treatments (e.g., radiation, further injections) to prevent recurrence. Prevention is key for keloids [8].

Medical Disclaimer

The information provided in this article is for educational purposes only and is not intended as medical advice. Always consult with a qualified healthcare professional for any health concerns or before making any decisions related to your health or treatment.

References

[1] Healthline. (2022, December 20). Keloid vs. Hypertrophic Scar: What"s the Difference?. [https://www.healthline.com/health/keloid-versus-hypertrophic-scar](https://www.healthline.com/health/keloid-versus-hypertrophic-scar)

[2] Cleveland Clinic. (2021, June 1). Hypertrophic Scar: What Is It, Causes, Treatment. [https://my.clevelandclinic.org/health/diseases/21466-hypertrophic-scar](https://my.clevelandclinic.org/health/diseases/21466-hypertrophic-scar)

[3] DermNet. (n.d.). Hypertrophic Scars and Keloids: A Complete Overview. [https://dermnetnz.org/topics/keloid-and-hypertrophic-scar](https://dermnetnz.org/topics/keloid-and-hypertrophic-scar)

[4] The Plastics Fella. (2021, March 14). Hypertrophic vs. Keloid Scar. [https://www.theplasticsfella.com/hypertrophic-vs-keloid-scar/](https://www.plasticsfella.com/hypertrophic-vs-keloid-scar/)

[5] NIH. (1994). Morphological and immunochemical differences between keloid and hypertrophic scar. [https://pubmed.ncbi.nlm.nih.gov/8030742/](https://pubmed.ncbi.nlm.nih.gov/8030742/)

[6] Mayo Clinic. (2023, July 13). Keloid scar - Diagnosis and treatment. [https://www.mayoclinic.org/diseases-conditions/keloid-scar/diagnosis-treatment/drc-20520902](https://www.mayoclinic.org/diseases-conditions/keloid-scar/diagnosis-treatment/drc-20520902)

[7] American Academy of Dermatology (AAD). (n.d.). Keloid scars: Causes. [https://www.aad.org/public/diseases/a-z/keloids-causes](https://www.aad.org/public/diseases/a-z/keloids-causes)

[8] Dermatology Seattle. (2025, October 20). Keloids and Hypertrophic Scars Prevention and Treatment Strategies. [https://dermatologyseattle.com/keloids-and-hypertrophic-scars-prevention-and-treatment-strategies/](https://dermatologyseattle.com/keloids-and-hypertrophic-scars-prevention-and-treatment-strategies/)

The Histological Differences Between Keloids and Hypertrophic Scars

While keloids and hypertrophic scars appear similar clinically, they have distinct microscopic features that explain their different behaviors.

Collagen architecture:

• Hypertrophic scars: Contain nodular structures of α-smooth muscle actin-positive myofibroblasts surrounded by thick collagen bundles arranged in a wavy, parallel pattern. This organized architecture allows for eventual scar maturation.
• Keloids: Contain thick, disorganized, randomly oriented collagen bundles (often described as "keloidal collagen" or "glassy collagen"). The collagen fibers are larger in diameter and more haphazardly arranged than in hypertrophic scars.

Cellular differences:

• Keloid fibroblasts have higher proliferation rates, greater collagen synthesis, and greater resistance to apoptosis than hypertrophic scar fibroblasts.
• Keloid tissue contains more mast cells, which release histamine and other mediators that stimulate fibroblast activity — explaining the intense itching associated with keloids.
• Hypertrophic scars contain more myofibroblasts, which are responsible for wound contraction.

Vascular differences:

Both scar types are hypervascular, but keloids show more pronounced angiogenesis and vascular disorganization.

Clinical Differentiation: A Systematic Approach

Distinguishing keloids from hypertrophic scars is essential for treatment planning, as they respond differently to interventions.

Key differentiating features:

The "beyond the wound" test:

The single most reliable clinical criterion for keloid diagnosis is extension beyond the original wound boundaries. If a scar is confined to the wound area, it is a hypertrophic scar regardless of its size or symptoms.

The "regression test":

Hypertrophic scars typically begin to flatten and soften within 6–12 months of formation, with most showing significant improvement by 2 years. Keloids do not spontaneously regress and may continue growing for years.

Scar Assessment Tools Used in Clinical Practice

Several validated tools are used to assess scar severity and track treatment response:

Vancouver Scar Scale (VSS):

The most widely used scar assessment tool in clinical research. Scores four parameters:

• Vascularity (0–3): Normal to purple
• Pigmentation (0–3): Normal to hyperpigmented
• Pliability (0–5): Normal to contracture
• Height (0–3): Flat to >5mm

Total score ranges from 0 (normal skin) to 14 (worst possible scar).

Patient and Observer Scar Assessment Scale (POSAS):

A two-component scale with separate observer and patient ratings. The patient component captures symptoms (pain, itching) and appearance concerns that the observer component may miss.

Manchester Scar Scale:

A 5-parameter scale assessing color, matte/shiny surface, contour, distortion, and texture.

These tools are primarily used in research settings but can help track your own scar's progress over time.

The Role of Skin Tension in Scar Formation

Mechanical tension is a critical determinant of whether a wound heals with a flat scar, a hypertrophic scar, or a keloid.

Lines of tension:

Langer's lines (also called cleavage lines) represent the natural orientation of collagen fibers in the dermis. Wounds that run parallel to Langer's lines heal with less tension and produce better scars. Wounds that cross Langer's lines at right angles are under greater tension and are more likely to produce hypertrophic scars.

High-tension anatomical sites:

• Presternal (chest) area: Subject to respiratory movement and pectoral muscle tension
• Shoulder: Subject to arm movement and deltoid tension
• Upper back: Subject to trapezius and rhomboid tension
• Knee and elbow: Subject to flexion-extension forces

These are the same sites most prone to keloid formation, supporting the role of tension in keloid pathogenesis.

Tension-reducing strategies:

• Steri-strips and wound closure tapes: Applied perpendicular to the wound to reduce tension during healing
• Pressure therapy: Compression garments apply counter-pressure that reduces tension in the dermis
• Silicone sheeting: May reduce tension through hydration and mechanical effects
• Surgical technique: Z-plasty and W-plasty redistribute wound tension along multiple directions

Psychological Impact of Keloids and Hypertrophic Scars

The psychological burden of visible scars — particularly keloids on the face, neck, and hands — is often underestimated by healthcare providers.

Prevalence of psychological distress:

Studies consistently find high rates of anxiety, depression, and body dysmorphic concerns in patients with keloids:

• A 2019 study in the Journal of the American Academy of Dermatology found that 40% of keloid patients met criteria for clinically significant anxiety.
• Body image dissatisfaction was reported by 67% of keloid patients in a 2021 survey.
• Social avoidance and reduced quality of life were common, particularly for keloids on visible body areas.

The itch-scratch-anxiety cycle:

Keloid itching is often worst at night and during stress. Scratching provides temporary relief but can traumatize the scar, potentially stimulating further growth. Anxiety about the keloid can amplify itch perception through central sensitization. Breaking this cycle requires both physical treatment (antihistamines, topical treatments) and psychological support.

Seeking psychological support:

Cognitive-behavioral therapy (CBT) has been shown to improve body image and quality of life in patients with visible skin conditions. Dermatologists should routinely screen for psychological distress and refer appropriately.

Pediatric Considerations

Keloids and hypertrophic scars in children require special consideration:

Ear piercing:

Earlobe keloids are the most common keloid in children and adolescents, almost always following ear piercing. The risk is highest in the first 1–2 years after piercing. Parents should be counseled about keloid risk before ear piercing, particularly in children with a family history.

Acne keloids:

Acne on the chest and back can trigger keloid formation in predisposed individuals. Aggressive acne treatment to prevent deep inflammatory lesions is important in keloid-prone adolescents.

Treatment considerations in children:

• Intralesional corticosteroids are used with caution in children due to growth effects with repeated systemic absorption
• Silicone sheeting is safe and effective in children
• Surgical intervention is generally deferred until adulthood when possible, as keloids may stabilize with age

Frequently Asked Questions

Q: Can a hypertrophic scar turn into a keloid?

A: No. Hypertrophic scars and keloids are distinct entities that develop from the same wound through different pathological processes. A hypertrophic scar will not transform into a keloid, though both can occur in the same patient.

Q: I have a scar that looks raised but hasn't grown beyond the wound. Is it a keloid?

A: If the scar is confined to the original wound area, it is most likely a hypertrophic scar, not a keloid. Hypertrophic scars can be quite raised and symptomatic but do not extend beyond wound boundaries. Most hypertrophic scars improve significantly within 1–2 years.

Q: Why do keloids affect darker skin tones more?

A: The exact mechanism is not fully understood. Melanocytes in darker skin produce more melanin and may interact differently with fibroblasts. Some research suggests that melanocyte-stimulating hormone (MSH) may stimulate fibroblast activity. Genetic variants associated with keloid susceptibility are more prevalent in populations of African, Asian, and Hispanic descent.

Q: Can I get a keloid from a tattoo?

A: Yes. Tattooing involves repeated needle punctures that can trigger keloid formation in susceptible individuals. People with a personal or family history of keloids should be cautious about tattoos, particularly on high-risk body areas (chest, shoulders, upper back).

Treatment Approaches: How the Differences Guide Therapy

The distinction between keloid and hypertrophic scars is clinically important because they respond differently to treatment.

Corticosteroid injections:

Intralesional triamcinolone acetonide is first-line treatment for both scar types. However:

• Hypertrophic scars respond more reliably (60–100% improvement)
• Keloids have more variable response (50–80% improvement) and higher recurrence rates
• Keloids often require more frequent injections and higher doses

Surgical excision:

• Hypertrophic scars: surgery alone has good outcomes; recurrence is uncommon
• Keloids: surgery alone has 45–100% recurrence rate; must be combined with adjuvant therapy (radiation, corticosteroids, pressure therapy)

Pressure therapy:

Continuous pressure (20–25 mmHg) for 12–24 hours/day for 6–12 months. More effective for hypertrophic scars (particularly burn scars) than keloids.

Silicone gel sheets:

Applied daily for 12+ hours. Effective for both types; better evidence for hypertrophic scars. Mechanism: hydration and occlusion reduce scar thickness and redness.

Laser therapy:

• Pulsed dye laser (585/595 nm): reduces redness and thickness; better evidence for hypertrophic scars
• Fractional CO2 laser: improves texture and pliability; used for both types
• Nd:YAG laser: penetrates deeper; useful for darker skin types

Radiation therapy:

Adjuvant radiation after surgical excision reduces keloid recurrence to 10–20% (vs. 45–100% with surgery alone). Concerns about long-term radiation risks limit use to adults with refractory keloids.

Genetic and Racial Factors in Keloid Formation

Keloids have a strong genetic component and disproportionately affect certain racial groups.

Racial prevalence:

• African, Hispanic, and Asian populations: 5–16% prevalence
• Caucasian populations: < 1% prevalence
• The higher prevalence in darker-skinned populations is not fully explained but may involve differences in melanocyte activity, TGF-β signaling, and immune responses

Genetic factors:

• Keloids run in families; autosomal dominant inheritance with variable penetrance has been proposed
• Multiple genetic loci have been associated with keloid susceptibility
• Genes involved in TGF-β signaling, collagen production, and apoptosis regulation are implicated

Hormonal influences:

Keloids are rare before puberty and after menopause, suggesting hormonal influences. Pregnancy can cause existing keloids to enlarge. Estrogen may promote fibroblast activity and collagen production.

Psychological Impact and Quality of Life

Keloids and hypertrophic scars — particularly on visible areas (face, neck, chest) — can significantly affect quality of life:

• Body image concerns and reduced self-esteem
• Social anxiety and avoidance
• Depression (more common with facial scars)
• Pruritus (itching) and pain affecting sleep and daily activities
• Restriction of movement (hypertrophic scars over joints)

Psychological support should be part of comprehensive scar management, particularly for patients with extensive or visible scars.

Frequently Asked Questions

Q: Can I prevent a keloid from forming after surgery?

A: Risk reduction strategies include: minimizing wound tension (use of deep sutures, wound closure tape), avoiding unnecessary procedures in keloid-prone areas, using silicone gel sheets starting 2 weeks after wound closure, and considering prophylactic corticosteroid injections in high-risk patients. No strategy eliminates keloid risk entirely in predisposed individuals.

Q: Will my keloid keep growing forever?

A: Keloids typically grow for months to years before stabilizing. Untreated keloids rarely resolve spontaneously. Treatment can reduce size and symptoms, but complete elimination is difficult. Recurrence after treatment is common, particularly with surgery alone.

Q: Is there a cure for keloids?

A: No single treatment cures keloids reliably. Combination approaches (surgery + radiation or surgery + corticosteroids) achieve the best outcomes. Emerging treatments (anti-TGF-β agents, anti-IL-13 biologics) are under investigation and may improve outcomes in the future.