Keloid formation is least likely seen over :

Keloids can result from surgery, burns, skin inflammation, acne, chickenpox, zoster, folliculitis, lacerations, abrasions, tattoos, vaccinations, injections, insect bites, ear piercing, or may arise spontaneously. Keloids tend to occur 3 months to years after the initial insult, and even minor injuries can result in large lesions. They vary in size from a few millimeters to large, pedunculated lesions with a soft to rubbery or hard consistency. Although they project above surrounding skin, they rarely extend into underlying subcutaneous tissues. Ceain body sites have a higher incidence of keloid formation, including the skin of the earlobe as well as the deltoid, presternal, and upper back regions. They rarely occur on eyelids, genitalia, palms, soles, or across joints. Keloids rarely involute spontaneously, whereas surgical intervention can lead to recurrence, often with a worse result. Ref : Barbul A., Efron D.T. (2010). Chapter 9. Wound Healing. In T.R. Billiar, D.L. Dunn (Eds), Schwaz's Principles of Surgery, 9e.