ALK-negative IMTs (44%) occurr in older patients (mean age 20.1) years and had greater nuclear pleomorphism, atypia, and atypical mitoses. In a series, all 6 metastatic IMTs were ALK-negative. (17414097)
Absent ALK expression is associated with a higher age overall, subtle histologic differences, and death from disease or distant metastases (in a younger subset). (17414097)
References
Inflammatory myofibroblastic tumor: comparison of clinicopathologic, histologic, and immunohistochemical features including ALK expression in atypical and aggressive cases. Coffin CM, Hornick JL, Fletcher CD. Am J Surg Pathol. 2007 Apr;31(4):509-20. PMID: 17414097