the scar tissue can occur in any site of the body after trauma, or like granuloma 

but keloid just occur in the skin area, in my knowledge 

thanks Shu-Hung Huang :)

then, it's about gene expression or the internal environment prevent the formation of keloid? 

That's a question that would be fiendishly-difficult to answer.  We know that scar can occur in any body site, but whether or not any of those scars could constitute "keloid" is really hard to prove, given the differences in tissue properties and physical environment, between skin and, say, peritoneum.  It would likely require biopsy and diagnosis based on histological features, or gene expression.  Even this may be misleading, as differences in intercellular tension/forces could alter gene expression and overt phenotype - even histological appearance.  Ethical approval for such a study also would be difficult to obtain.

The real problem in answering this, is that there is really no good animal model for keloid.  Recently reported studies used explanted human cells into immuno-incompitent animals, eg athymic mice (Wang & Luo, J Burn Care Res 2013, 34: 439-46).

Good luck with your endeavours!

thanks Ciaran O'Boyle...

yaa, 'til now i still can't figure what method used to study keloid

Keloid formation depends on specific skin cells production and skin matrix disorganization, it is not correct to talk about "keloid"  under the subcutaneous level. By the other hand, f course it is posible to consider cicatricial hypertrophy (which is not the same, for instance, in terms of type of collagen deposed and orientation of its fibers) at the visceral level.

thank you Cabral Luis for your explanation ^_^

Keloids are characterized by fibrotic tissue. The scarring is overwhelming and atypical fibroblasts produce massive amounts of collagen type III, that is later replaced by collagen type I. In other words keloids are  "benign tumors" that originate from a skin wound. I fully agree to Luis Cabral and his comments on the matrix disorganization and the cutaneous localisation. Scarring can occur anywhere in the human body, also hypertrophic scaring, which has to be differentiated from keloids. Hypertrophic scars are limited to boundaries of the scar, whereas keloids are not. 

I am in agreement with Cabral Luis and Jan Plock re. keloids occurring in skin only (as far as it is known). 

Interestingly, I remember reading that keloids don't occur only in cases of trauma, but may be spontaneous, also.  Of course, the former is far, far more common!

I think we cannot assume keloids appear "spontaneously", the most probable reason for these aparent idiopatic cases is minor trauma, mostly unnoticed by the patients

The scar is characterized by proliferation of connective tissue, mainly collagen fibers in areas of cell destruction. The keloid is a scar defective; exhibits excessive amount of collagen, grows beyond the boundaries of the original wound and not regress. This problem occurs more often in african-Americans and Asians.

Though I am inclined to agree with you, Cabral, there are multiple reports of 'spontaneous' keloid-formation that can be found on PubMed, et.c..  For example: 

http://www.journalmc.org/index.php/JMC/article/viewFile/1887/1224 

(I am just reporting what our colleagues have written!)

"Confirmed instances of spontaneous keloid have been reported in Dubowitz syndrome, Rubenstein–Taybi syndrome and Noonan syndrome." 

http://www.journalmc.org/index.php/JMC/article/viewFile/1887/1224

keloids and hypertrophic scars are peculiar to the skin,they do not occur inside the body example the organs like stomach,liver ,lungs etc,probably here in lies the answer to controll keloids,one thing is the continuously moist environment.....good luck

thanks all, for bunch of information  ^_^

Dear Wardani, keloids by definition is a collagen overproduction beyond the lesion and here is the difference between keloids and scar which is limited to lesion even in hypertophic type. Keloids are also recorded in association

with EDS, pachydermoperiostosis and Rubinstein–Taybi

syndrome. Keloid fibroblasts, unlike those from hypertrophic scar tissue, are hyperresponsive to both TGF-β, which is abundant in healing wounds,

and PDGF. Keloid fibroblasts in culture secrete increased amounts

of collagen and glycosaminoglycans for several passages in tissue culture. It is unclear whether these cells represent a normal subgroup or have undergone transformation. Altered expression of proteoglycans in keloids may

affect the three-dimensional organization of collagen fibres. Malignant degeneration has been reported, although a fibrosarcoma can mimic keloid clinically. So nothing to prove its presence or not in other organs than skin!?

thank you very much, Bashir. very helpful :D

would youmind to help me for the reference(s)? heheh

Rooks text book of Dermatology 7th edition Keloids and hypertrophic scars, 46.54

thank you bashir :D

Is their any evidence that keloid invades normal skin, or is it just that it expands from the point of original insult?

mmm... i thought it's both expand and invades normal skin. some keloid has slop-like end (invade) an some has cliff-like end (expand). but i'm not really sure

Hello Anggadia, I discovered your post today (two years too late) while researching a strange case of keloid-like scars in the lung. Besides all that has been said so far, it is important to know that, under the microscope, keloids have a characteristic and diagnostic histological appearance and are, therefore, a different form of scar. Not everyone makes keloids; they are the result of individual susceptibility inherited in an autosomal-dominant trait (OMIM #148100). Finally, a rare lung condition called Pulmonary hyalinizing granuloma is collagenous nodules forming in the lung with a histological appearance identical to skin keloids.

Keep asking questions!

Wow thank you for such detailed answer Emmanuel. It's never been to late to share knowledge :)

So can a surgical removal of a fibroid of a person who is prone to keloids cause further fibroid formation like removing a keloid scar from a keloid prone skin? I am asking to help with a clinical decision I have to make.

Dear Dizon, in cases of Dermatofibroma, surgical excision in normal person no further fibroid happen again , in a keloids prone persons ( As it is known more prevalent in blacks) the same like normal skin.

So Dr. Bashir, are fibroids the same like normal skin or keloid prone skin that if one surgically removes a fibroid then it can grow back and probably even be bigger in size?

Dear Dizon, I was thinking that most fibroids may be due to keloid formation or hypertrophy scars because some fibroids occurs post exposure to trauma but the question will now be what's responsible for hormonal and menstrual changes in such patients?

Thank you for answering my question. I really appreciate it.

Nathalie Dizon, large keloids are treated by surgical excision followed by injection of corticosteroids drugs into the new scar, compression and/or radiotherapy. These post-operative treatments reduce the risk that the new scar will itself become a keloid. I hope this helps.