Thanks for writing to HCM
You didn't mentioned type of cancer she had on her leg. Some primary cancer can metastasize to lungs.
Your mother also had history of smoking
, so lung cancer
can't be ruled out.
All probabilities have to be confirmed by imaging.
Not the least it can be infective also.
So, she needs chest-ray( PA) and Contrast CT Scan
Treatment depends upon findings of investigations and clinical examination.