Stretch marks or striae, are a form of scarring on the skin
caused by tearing of the dermis. This could be due to rapid stretching of the skin
associated with rapid growth , weight gain or during rapid muscle growth. Stretch marks can appear anywhere on the body, especially in places where larger amounts of fat are stored such as the abdomen, breasts, upper arms, underarms, thighs (both inner and outer), hips, and buttocks. This includes the skin going to your groin but not your scrotum.