[Gastrointestinal inflammatory myofibroblastic tumor: a clinicopathologic study]

Objective: To study the clinicopathologic characteristics, immunophenotype and ALK gene alterations of gastrointestinal inflammatory myofibroblastic tumor. Methods: Clinical data, histological features and immunohistochemical results were analyzed in 7 cases of gastrointestinal inflammatory myofibroblastic tumor at Zhejiang Province Taizhou Hospital from January 2005 to December 2016. ALK gene status was investigated by ALK fluorescence in situ hybridization. Results: There were 4 female and 3 male patients. The age of patients ranged from 1 to 72 years (median age=53 years and mean age=40 years). The tumor was located in stomach (n=4), left hemicolon (n=1), right hemicolon (n=1) and rectum (n=1). Histologically, the tumors consisted of spindle fibroblast and myofibroblast cells growing in bundles with inflammatory infiltration primarily composed of plasma cells and lymphocytes. Immunohistochemical study showed spindle tumor cells were positive for vimentin (7/7), SMA (7/7), but were negative for CD34, CKpan, CD117, DOG1, S-100 and desmin. Two cases expressed ALK protein and fluorescence in-situ hybridization revealed the presence of ALK gene rearrangement in the both cases. Conclusions: Gastrointestinal inflammatory myofibroblastic tumor is a rare neoplasm that is easily misdiagnosed. Its surgical removal is a reliable treatment. ALK may be a potential novel therapeutic target for inflammatory myofibroblastic tumor.