ALK-positive inflammatory myofibroblastic tumor harboring ALK gene rearrangement, occurring after allogeneic stem cell transplant in an adult male

Inflammatory myofibroblastic tumor arose as a defined neoplasm from the disparate group of tumors (both neoplastic and inflammatory) originally described as inflammatory pseudotumors. The morphologic features are well described, and 50-60% of cases are associated with fusions of the anaplastic lymphoma kinase (ALK) gene. We describe an inflammatory myofibroblastic tumor in the lower abdominal wall of an adult male, which occurred 88 days after he received an allogeneic stem cell transplant for T-lymphoblastic lymphoma, and which was positive for ALK immunohistochemistry and showed ALK gene rearrangement by fluorescence in situ hybridization. Two other cases are reported in the post-stem cell transplant setting, but both occurred in children and did not have molecular analysis performed. The etiology remains unclear, but may be due to immune dysregulation caused by any combination of prior chemotherapy, radiotherapy and immune suppression. These neoplasms should be considered as a rare consequence of allogeneic stem cell transplantation and referral to a specialist sarcoma center for further management may be required.