ETV6-NTRK3–Positive Inflammatory Myofibroblastic Tumor of the Ileum: Report of an Infantile Case and Review of the Differential Diagnosis of Pediatric Intestinal Polypoid Lesions

We report a case of an intestinal polyp causing intussusception in a 2-month-old boy. The resected polyp was diagnosed by histology and immunohistochemistry as an anaplastic lymphoma kinase (ALK)–negative inflammatory myofibroblastic tumor (IMT), and the ETS variant 6 (ETV6)–neurotrophic receptor tyrosine kinase 3 (NTRK3) fusion gene was detected by reverse transcription–polymerase chain reaction. Recently, histologically definitive, ALK-negative IMTs possessing the ETV6-NTRK3 fusion gene have been reported. To the best of our knowledge, this is the first case of an intestinal IMT harboring ETV6-NTRK3. In the differential diagnosis of ALK-negative IMTs or spindle cell lesions showing considerably high cellularity, ETV6 rearrangement should be considered.