Lung liason

I had an abdominal CT scan which was fine but the radiologist spotted a small liason(1cm x .8 cm) on my lung. A second scan six weeks later showed no change in the size of the liason but the radiologist could not say for sure that it was scar tissue.  Today I saw a specialist who has recommended a PET scan to finally determine whether or not it is cancer.  He said that at first glance it doesn't appear to be cancer and that it is too small to get an absolutely clear biopsy.  What is the chance that it is cancer?  I have no symptoms and am a 51 year old female non-smoker who is in otherwise good health.