Abstract: Objective  To explore the application of polarizing microscope in the diagnosis of tracheobronchial amyloidosis, in order to reduce the rate of misdiagnosis. Methods  A total of 13 pathological sections positive for Congo red were re-observed, and 104 cases reported since 1987 which had complete clinical data and implicit pathological Results   were analyzed. Results  Of the 13 pathological sections, 8 showed apple-green birefringence when viewed under polarizing microscope. If the diagnosis of amyloidosis was based on Congo red staining only, it would result in 39.5% false positive cases, which might indciate that 40 cases might be misdiagnosed among the 104 confirmed cases. Conclusion  Only when both Congo red staining and polarizing microscope show positive Results  ,  can we diagnose the case as PTBA.

Key words: Primary tracheobronchial amyloidosis, Polarizing microscope, Misdiagnosis, False positive;