The positive bronchus sign is seen on CT chest, and refers to the presence of a bronchus leading directly to a peripheral lung lesion 1,2.
In one study, four types of tumor-bronchi relationships were described 3:
- patent bronchus leads directly to the tumor mass
- bronchus is within the tumor mass
- bronchus is compressed and narrowed by the tumor, but the bronchial mucosa is intact
- bronchus communicates directly with the tumor, but the proximal bronchus is narrowed by peribronchial or submucosal spread of the tumor or by enlarged lymph nodes, limiting access to the distal neoplasm
The first two relationships are favourable for transbronchial biopsy. The positive bronchus sign may help to predict whether bronchoscopy and transbronchial biopsy can facilitate the histological diagnosis of the nodule on the basis of the likelihood of recovering a tissue sample 1,2. The presence of this sign at CT indicates that a higher yield of peripheral nodular mass can be obtained at bronchoscopic biopsy; in patients who do not have this sign, transthoracic needle biopsy is a better method for obtaining tissue sample.
- 1. Singh SP. The positive bronchus sign. (1998) Radiology. 209 (1): 251-2. doi:10.1148/radiology.209.1.9769839 - Pubmed
- 2. Ernst A, Anantham D. Bronchus sign on CT scan rediscovered. (2010) Chest. 138 (6): 1290-2. doi:10.1378/chest.10-0892 - Pubmed
- 3. Tsuboi E, Ikeda S, Tajima M, Shimosato Y, Ishikawa S. Transbronchial biopsy smear for diagnosis of peripheral pulmonary carcinomas. (1967) Cancer. 20 (5): 687-98. Pubmed