Why does the diagnostic staging of lung cancer change from time to time?

Why does the diagnostic staging of lung cancer change from time to time?

Lung cancer staging changes because the clinical stage and the pathologic stage may be different. The clinical stage is defined by what we see radiographically. But the presence of tumor in certain areas may not necessarily turn out to be cancer at the end. So, what we often refer to as a pathologic stage, whereafter a biopsy procedure is done, either surgically or by less invasive way. This is the goal standard to stage a patient. Staging sometimes changes from a clinical to pathologic staging, because what we see by radiologic studies does not necessarily turn out to be cancer in those areas.