Objective  To investigate the clinicopathological features and key points in diagnosis and differential diagnosis of adenoid cystic carcinoma of the upper trachea.

  Methods  From January 2000 to February 2014, 4 cases of adenoid cystic carcinoma of the upper trachea were diagnosed in Peking Union Medical College Hospital. Microscopic, immunohistochemical, and histochemical staining results of the patients were reviewed to summarize the clinicohistological and immunohistochemical features as well as key points of diagnosis and differential diagnosis of adenoid cystic carcinoma of the upper trachea.

  Results  The 4 patients of adenoid cystic carcinoma of the upper trachea included 1 male and 3 females, aged 38-57 years (mean age 47 years). None had history of adenoid cystic carcinoma, and one had the history of nodular goiter surgery. Microscopically, 4 cases all appeared as cribriform/tubular type, with thyroid tissue involvement in 3 cases, nervous tissue involvement in 3 cases, and no lymph node involvement. Immunohistochemically, P16, CD117, BCL-2, P63, SMA, and type Ⅳ collagen were positive in all 4 patients, average Ki-67 index was 8%, and TTF-1 and P53 were negative in all patients. Histochemically, AB/PAS was positive in all patients. All the 4 cases received postoperative radiotherapy (total dose 48-56 Gy) and were followed up for 6-120 months (mean 72.5 months). One case had relapse after 96 months, and the other 3 had no recurrence or metastasis during the follow-up period.

  Conclusions  Adenoid cystic carcinoma of the upper trachea is a rare low-grade malignant tumor. It is slow-growing and the majority of patients have invasion of thyroid tissue at presentation. It has to be differentiated from primary thyroid cancer, especially in fine-needle aspiration cytology and intraoperative frozen section of the thyroid. Accurate diagnosis can be made based on laryngotracheoscopical findings, typical morphological, immunohistochemical and histochemical features. Complete resection of the tumor is hard to achieve, therefore radiotherapy may be useful to prevent recurrence.