x ray results

I am really worried for my mum she is a smoker ,she has had a persistant cough for a couple of months she also has asthma .The doctor sent her for a x ray which has shown a shadow on her upper right chest(not to sure if it is chest or lung) ,because she has never had an x ray before in her life they are going to wait 4 weeks from her first x ray then she has to go back for a second x ray to compare .The x ray has also shown an enlarged heart is there treatment for an enlarged heart ?. The doctor has said to my mum at this time they really dont know what this shadow is ,she did say if its still there after second x ray they may do a biospy .Cancer is always a worry so im thinking the worst at the moment .Do you think the doctor suspects cancer ,would they have left my mum 4 weeks if it could be cancer ? but they have said they have to wait 4 weeks to compare x ray results .Should they have not sent her for a ct scan ? So we have to wait now 4 weeks until she has second x ray not knowing what is happening .Any advice would be appreciated .