Table I.

Differences between hypertrophic and keloid scars.

	Hypertrophic scar	Keloid scar
Clinical appearance	Develops soon Stays within the original scar boundary Improves with time Tends to flatten with time Appears when scars cross joint, skin creases at a right angle No association with skin color	May appear after months Grows beyond the boundaries of the initial wound Rarely improves, usually develops with time Raised, firm, pruritic, painful Do not spontaneously regress Occurs on the ear lobe, sternal notch, shoulders, upper back, back of the neck, cheeks Associated with dark skin
Histopathologhical	Collagen fibers oriented parallel to the long axis of the epidermal surface Nodules of high density fibroblasts and collagen in the middle or deeper scar’s layer Small blood vessels oriented vertically around the nodules 20–30% mast cells in reticular dermis	“Keloid collagen” (thick and hyalinized collagen) arranged in a hazard pattern Absence of nodules Small blood vessels under die epidermis appearing to grow out in the scar 73% mast cells in reticular dermis
Immunohistochemical	No α-SMA expressing myofibroblasts	α-SMA expressing myofibroblasts present in a third of cases Higher CD4(+):CD8(+) ratio
Electron microscopic		The collagen fibers separated from the fibroblast’s membrane by a amorphous substance