MSRA-1000

A 36-year-old woman comes to the clinic with a lump in her left breast. She has recently lost approximately 1.5 stone in weight by attending a weight loss program. During the examination, a firm lump is detected in her left breast that is not mobile but not attached to the underlying muscle. She recalls being hit by a squash ball in this area a few months ago. What is the probable reason for her lump?