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Xu et al. Radiation therapy in keloids treatment

INTRODUCTION the Latin word “crab”. However, the hypertrophic scars
are apparently more linear, nodular, or papular with
Keloids have been considered frustrating issues more regular borders and are always within the original
for many decades since surgeries evolved. The wound borders.
keloids were firstly considered as pathological wound
healing process. Deemed as benign tumors, keloids The hypertrophic scars usually occur 4 to 8 weeks
were uncontrolled and unconfined sharply bounded postoperatively or after the injury, compared to high
hyperplasia of dermal connective tissues arising from variability of keloids formation time. The time of keloid
an abnormal wound healing process. This benign formation can be quite volatile, from generally within
lesion often follows dermal injury, burn injury, tattooing 3 months to many years after the dermal injury. Unlike
and even simple acnes. However, the cause of keloid the hypertrophic scars, which often gradually regress
formation remained a mystery. Familial tendency after years, keloids persist for longer period of time and
and darker skin races preference were observed do not regress spontaneously. Moreover, even both
in prevalence of this benign disease. The keloid is lesions are pruritic, the keloids are more likely to cause
[1]
gradually considered as a genetic disease with genetic significant pain and hyperesthesia.
predisposition that demonstrates an autosomal
dominant or X-linked inheritance pattern. Even PATHOPHYSIOLOGICAL BASIS OF
though there was no specific genes identified directly KELOIDS FORMATION
related to keloid formation, several susceptibility loci
were reported before. In one study utilizing genome- Keloids can derive from any form of dermal injury.
wide sequencing technology to discover susceptible However, the pathological process of its formation
loci, 4 potential single-nucleotide polymorphisms in is still poorly understood. Both environmental and
3 chromosomal regions in Japanese patients were genetic factors contribute to this pathological process.
identified. Two rare syndromes were historically Apparently, a universally accepted theory is that both
[2]
named due to its familial tendency, the Rubinstein- keloids and hypertrophic scars are considered results
Taybi syndrome and Goeminne syndrome.
of persistent chronic inflammation. In histological
Black people are more likely to have this benign view, continuous local inflammation was observed
along with keloid progression. Inflammatory cells,
[6]
lesion, while the Caucasians are least likely. In African increased numbers of fibroblasts, angiogenesis, and
populations, the incidence is 6-16%, which is 15 times
higher than whites. The more piercing happened new collagen deposition were all observed. Besides,
[3]
among women might bring the confounding bias which inflammatory cytokines or mediators were also
leads to female predominance. [4] overproduced in keloids or hypertrophic scar tissues,
including interleukin (IL)-1α, IL-1β, IL-6, and tumor
Moreover, keloid growths are more likely seen on necrosis factor (TNF)-α. These pro-inflammatory
the chest, shoulders, upper back, back of the neck genes or products are believed to be sensitive to
and earlobes, where larger skin tension should be trauma, induce continuous inflammation and collagen
noted. Notably, the earlobe is exceptional, which deposition. Moreover, persistent chronic inflammation
indicate lower recurrence rate under similar treatment. could potentially explain the relative higher
Therefore, this site-specific characteristic provides us invasiveness of keloid scars. The major occasion
the site-specific treatment algorithms, for example, where inflammation happened, reticular dermis is
to decide whether or not the lesion requires radiation believed to function primarily in keloid formation. This
therapy. There were several characteristics of keloids, theory is partly supported by the valid therapeutic value
several morphological and histological differences. It is of corticosteroids injection/tape/ointment in keloid
also noted that, the hypertrophic scarring and keloids treatment. Besides, one of the many widely accepted
often confuse dermatologists and surgeons when it theories is that more injury and inflammation will more
comes to diagnosis due to their similar appearances. likely generate excessive scar tissue. A multitude of
cells were involved in wound healing process, as well
Clinically, keloids are firm nodules, which can be skin as keloid scarring. One of the very important cells,
colored, dispigmented, or erythematous secondary to fibroblast produce collagen show sustained activity. [7]
telangiectasias. The keloid scars in Caucasian people, Aberrantly excessive growth factor and overproduction
are more likely to be erythematous and telangiectatic. of its receptors were both observed in growth pattern of
Comparatively, hyperpigmentation is more popular in keloid-derived fibroblasts. Overexpression of vascular
Blacks. The lesion always extends beyond the border endothelial growth factor (VEGF), transforming growth
[5]
of dermacated primary lesion, and often with irregular factor (TGF)-β1, TGF-β2, connective tissue growth
shape, just like how the word “keloid” originated from factor, insulin-like growth factor (IGF)-1, as well as the
Plastic and Aesthetic Research ¦ Volume 4 ¦ July 28, 2017 117