What Causes Chest Soreness, Throat Pain And Breathlessness?

my daughter had been complaining about sore chest around her breast and it hasnt gone away, 2 days later i took her to the doctor as she said it started hurting towards her throat area and was getting hard to breathe at times. The doctor said it could be an inflammed sternum however i read up on what could cause this and she was doing absolutely nothing like those to bring on, she was doing absolutely nothing other than being a laid back teenager. Reason i ask if this could be what she has is so that we can understand what caused it and prevent it happening again?