Fatigue   
A feeling of tiredness and lack of energy, related to cancer or cancer treatment or both.

Fine needle aspirate   
A procedure in which a needle is inserted under local anesthesia to obtain a sample for the evaluation of suspicious tissue.

Fistula   
An abnormal opening between two areas of the body.

Five-year survival   
In the setting of lung cancer, this term is often synonymous with cure.

Flow cytometry   
A procedure that measures the amount of DNA in cells.

Frozen section   
A technique in which tissue is removed, then quick-frozen and examined under a microscope by a pathologist.