Lung lesion - Biopsy not conclusive

Hi
I am having for around 6 months now.
I have undergone a XRay chest 3 months back but it was normal.
So doctor suggested that it could be allergy because of pollution or it could be because of cold climate.
Recently i had undergone second XRay and CT Scan which showed a lesion in Right middle lung.
Doctor had done both bronchoscopy and CT guided biopsy but both were inconclusive.
Since both were not conclusive of malignancy , doctor was saying that it could be because of some infection.
He had taken antibiotic for some time and since it was not curing , i am taking Trial Anti Tuberclosis tablets now.
What could be the nature of infection and is there any way for diagnosis.
I am a non smoker and i am a software engineer and not exposed to pollution or smoke for a long time.

[National Jewish Health]

That the bronchoscopy showed no sign of malignancy, is very good news.  If the lesion was not evident on the first x-ray, but clearly evident on the second x-ray and not just on the CT scan that would also suggest that it is not a benign or malignant growth.  Infectious disease of the right middle lobe is common, but seldom caused by tuberculosis (TB).   But bronchial washing and sputum should be cultured for TB and routine culture.  More often the infection is caused by one of the more common bacteria that infect the lung, but it is not unusual for cultures to be negative.

If the right middle lobe (RML) lesion shows no sign of resolution in response to antibiotic and TB therapy, and especially if it is enlarging, the RML should probably be removed.

This is often a difficult decision and should best be made by a lung specialist.

Good luck.