Can you tell on a ct scan if it is lung cancer or something else? what reasons wouldn't a dr do a needle biopsy?

Trust your Dr.: Sticking a needle in anything is always risky. Your doctor will have to decide if the lesion on the cat scan looks suspicious enough to warrant that risk. Oftentimes we will recheck another cat scan in about six months to see if there has been an interval change. I would trust your doctors judgment on this.

Sometimes: Certain things appear on ct scan, have characteristics of an old scar. No biopsy is needed. Certain spots are too small, too far, too dangerous to reach with a needle.

High risk patient: If a mass looks suspicious on chestct scan, and the patient is high risk (current or former smoker, age >40) and surgery is an option, then a needle biopsy may not be necessary given the potential of a false negative.