hi, my mother had a mastectomy post chemo and had radiotherapy afterwards. 9-10 months have passed. She had her pet scan in september, 2017 which was all okey. Now she is having dry cough for more than one month. She had fever and cold in december, 2017. Now the cough is persistant. She have no pain but breathlessness to some extent while walking. she often have a low grade fever if she is exhausted. No other changes are there. She have no weight loss. Doctor has suggested pet scan to rule out if there is any problem with lungs. Her blood test reports, memmography and stomach ultrasound are normal. Can you suggest what it can be.