Prognostic factor vs. risk factor As far i understand the difference between Risk factor and Prognostic factor is :
Risk factor is the cause of a condition whereas Prognostic factor influences the outcome
who has the condition, like resectability of tumour for lung cancer.
Is that the case ?
Would you explain the difference with a similar example in both cases ?
 A: You are correct in that these terms are usually used in different settings.
(1) A risk factor is associated with the outcome of interest (causality is almost never assumed). Usually a disease.
(2) A prognostic factor is associated with the outcome of interest. Usually morbidity or mortality.      
Thus smoking (risk factor) is associated with lung cancer and tumor stage (prognostic factor) associated with lung cancer mortality. 
The other difference may be that risk factor models are different from prognostic models. The goals and the model building process usually differ. Most obviously the aim of the prognostic model is usually to provide the most valuable estimate of probability/prognosis while the risk factor model is trying to elucidate associations between potential risk factors and the process of interest. 
A: A risk factor is typically a variable thought to be related to the incidence of an outcome. Anylyses of risk factors usually center on trying to make reasonable causal inferences, to facilitate subsequent preventive efforts. 
A prognostic factor is typically a variable thought to be related to how a disease progresses, given you already have the disease. Analyses of prognostic factors tend to focus on making predictions, irrespective of any causal inferences.  
