Any growth in the lung should be investigated thoroughly to reach the diagnosis because lung malignancies are very common and outcome of treatment very guarded. That`s why an all out effort is made to establish the diagnosis. Since bronchoscopy
has not been successful your doctor has suggested thoracotomy
. But before that has a CT guided FNAC been attempted? This may help in reaching a diagnosis and avoid thoracotomy. Though thoracotomy has its inherent risks but with modern day advancement and in the hand of a good professional, they are minimal.