What Causes Dent On Outer Thigh?

Dear Dr. Rynne, Nearly 2 months or so back, I discovered a vertical medium-sized dent, on my outer left-thigh. The dent would be ~ 5 inches long and 2 inches wide. I have no pain in my thigh/ leg. However, about a week or so back, the skin covering the dent became somewhat coarse to touch. Now, the skin seems to be nearly ok now. I do not lean against anything, so cant explain the dent in any way! Do you have any idea regarding what the dent might be? My mother was diagnosed with breast cancer (in late 2012) and has got her mastectomy done. She is cancer free now. My aunt (mom s sister) is suffering from breast cancer. I am very tensed regarding what might be causing this dent. I m a 36 yr old Asian woman. Any help would be very much appreciated! Thanks a lot, Ed