Imaging findings of salivary gland-like neoplasms of the tracheobronchial tree

Objective: To assess the imaging features of salivary gland-like neoplasms (SGN) of the tracheobronchial tree, including adenoid cystic carcinoma (ACC) and muco-epidermoid carcinoma (MEC). Methods: Eighty-nine cases of SGN of the tracheobronchial tree were reviewed. There were 62 cases of ACC (male 33, female 29; age range, 20-73 years) and 27 cases of MEC (male 16, female 11; age range, 16-60 years). 40 cases of ACC and 18 cases of MEC had imaging materials before surgical treatment. For ACC, 33 cases had conventional radiograph and 21 cases had CT scan. For MEC, 17 cases had conventional radiograph and 6 cases had CT scan. Results: (1) Location: 37 cases of ACC were central type and most of them (26 cases) located at trachea, 3 cases were peripheral type. 13 cases of MEC were central type and mainly located at lobar bronchi (8 cases). 5 cases were peripheral type. Of the peripheral lesions, all except one ACC were located at the inner field of the lung adjacent to the hilus. (2) CT findings; Of the 18 cases of central type of ACC, there were intraluminal (3 cases), intra-and-extra luminal extension (14 cases, 8 cases with wall thickening), and infiltrative wall thickening (1 case) lesions. The attenuation of the tumor was lower or similar to that of the muscle in all of the plain scans and in 72.2% cases after contrast-enhancement. Infiltration of the adjacent tissue or organs was detected in 8 cases. Of the 6 cases of central type of MEC, there were intraluminal (5 cases) and intra-and- extra luminal extension (1 case) lesions. Marked enhancement of the mass (4 cases) of calcification (3 cases) were seen. The margin of MEC was well-defined, and no local infiltration was found. Conclusion: SGN of the tracheobronchial tree tended to be originated at major airways. ACC mostly located at trachea, whereas MEC located at lobar bronchi. Both had the manifestations of intraluminal, intra-and-extra luminal, and peripheral lesions adjacent to the hilus. ACC tended to have extra luminal extension and infiltrative wall thickening due to their invasive character. Low attenuation was shown in plain scan and with minimal enhancement after contrast administration. MEC mostly manifested as intraluminal type without infiltrative wall thickening, but with distinct enhancement. About half of the tumors had intratumoral calcification and mucous impaction could be identified