Adenoid cystic carcinoma in children and young adults: A clinicopathological study of 12 cases.

Objective: To investigate the clinicopathological characteristics, immunoprofile, and molecular alterations of adenoid cystic carcinoma (ACC) in children and young adults. Materials and methods: Twelve cases of ACC were included. MYB, MYBL1, Ki‐67, type IV Collagen, Laminin, and LAMB1 expression were detected by immunohistochemistry. MYB and MYBL1 rearrangements were detected by fluorescence in situ hybridization. Results: Among 12 patients, four were female and eight were male. Seven cases (58.3%) located in major salivary glands and eight cases (66.7%) were classified as Grade I. Ten tumors (83.3%) had collagenous and hyalinized stroma. MYB was positive in 83.3% cases, and the average Ki‐67 labeling index (LI) was 8.3%. LAMB1, type IV Collagen, and Laminin were positive in 91.7%, 66.7%, and 58.3% cases, respectively. Besides, three out of eight tumors had MYB rearrangement. Cases without MYB rearrangement were negative for MYBL1 expression and MYBL1 rearrangement. The average follow‐up time was 91.8 months. Four patients had recurrent diseases. Conclusions: ACC in children and young adults was seen more frequently in males and major salivary glands. Most cases had ECM and hyaline stroma. Grade III tumors, higher Ki‐67 LI, negative expression of type IV Collagen, and Laminin showed a tendency of higher recurrence rate. [ABSTRACT FROM AUTHOR]