Keloid Scar from nowhere

Hi,
I have had a keloid scar on the upper part of my calf muscle on the outside of the knee. I have had the scar from when I was about 12 or so (I am 28 now). The scar is about an inch long now and a third of an inch wide. I have some questions about this.
- I don't remember ever getting hurt there. With such a big scar, I think I would have remembered. Question: Can you get a keloid scar formation from no apparent injury or from a very minor injury?
- The scar has grown in size and I feel it has been growing. So I am now measuring it regularly. Question: Do Keloid Scars grow so many years after being first noticed?
- I was scared that it may be skin cancer and showed it to a friend who is a doctor, informally. He said since there is some hair growth on the scar itself, it is not likely to be and there is nothing to worry about. Question: Does sparse hair grow on the surface of keloid scars?
- Finally, it pains occasionally and I wanted to know if this is common.
I have attached a couple of pictures to give a better idea of the scar.
Thank to you all in advance for your help.
P

[Dr_Aparna]

Hi,
Scarring cannot occur prior to any injury.Scars are areas of fibrous tissue that replace normal skin (or other tissue) after injury. A scar results from the biologic process of wound repair in the skin and other tissues of the body. Thus, scarring is a natural part of the healing process.
In a person with this tendency even a minor injury can lead to keloid formation.
Keloid scars are a more serious form of scarring, because they can carry on growing indefinitely into a large, tumorous (although benign) growth.
Keloids consist of hard, raised scars that may be slightly pink or whitish. These may itch and be painful, and some keloids can grow to be quite large.
REF:http://www.answers.com/topic/keloid?cat=health