SN6 SHORT NOTE 5M ★ High-yield

Differentiate keloid from hypertrophic scar. Add a note on the pathogenesis of keloid.

Pathology · 2nd Professional — Para-Clinical

Definition

Keloid is an excessive, tumour-like scar that proliferates beyond the boundaries of the original wound and shows no tendency to regress.

Keloid Compared with Hypertrophic Scar

Feature	Keloid	Hypertrophic scar
Extent	Extends beyond the original wound margin	Remains within the wound margin
Onset	Delayed, months after injury	Within weeks
Natural history	Persists and may enlarge; does not regress	Often regresses over 1–2 years
Recurrence after excision	Very common — often worse	Uncommon
Collagen	Thick, haphazard, hyalinised "keloidal" bundles; type III predominates	Finer, arranged parallel to the surface
Site	Sternum, shoulder, upper back, ear lobe, jaw	Anywhere, especially across flexor surfaces
Contracture	Uncommon	Common
Racial predisposition	Marked — far commoner in dark skin	Less marked

CLINICAL PEARL

The distinction is entirely about the wound margin. A raised scar that stays within the original line is hypertrophic and will probably settle; one that creeps outward into normal skin is a keloid and will not. That single observation predicts both the natural history and the wisdom of operating.

Pathogenesis

Imbalance between collagen synthesis and degradation — synthesis is increased up to 20-fold and collagenase activity is reduced
Excess TGF-beta and other growth factors drive fibroblast proliferation
Fibroblasts are abnormally responsive and resistant to apoptosis
Genetic predisposition, with familial clustering and a strong racial association
Wound tension and prolonged inflammation are important local factors

Predisposing Factors

Dark skin — up to 15 times commoner, a considerable problem in Indian practice
Age 10–30 years; rare in the very young and the elderly
Sites of high skin tension — sternum, shoulder, upper back
Burns, acne, ear piercing, vaccination and surgical scars
Pregnancy and puberty, suggesting a hormonal influence

Applied Aspects

Prevention is far better than treatment — incisions along skin creases and lines of least tension, meticulous technique, and avoidance of unnecessary surgery in a predisposed patient
Intralesional corticosteroid is the first-line treatment, flattening the lesion by inhibiting collagen synthesis
Excision alone is contraindicated — recurrence is the rule and the result is often larger; excision must be combined with steroid injection, pressure or radiotherapy
Silicone gel sheeting and pressure garments are useful, particularly after burns
Ear-lobe keloids after piercing are among the commonest presentations, and respond well to excision with adjuvant treatment

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