The focus of this study was to investigate anaplastic lymphoma kinase (ALK) expression by immunohistochemistry using a highly specific antibody. Distribution and frequency of ALK expression may provide a clue for ALK inhibitor use in small round cell tumors of childhood. The study group involved 76 small round cell tumors of childhood, which composed of 11 rhabdomyosarcomas, 13 Wilms tumors, 7 Ewing sarcoma/primitive neuroectodermal tumors, 34 peripheral neuroblastic tumors, and 11 acute lymphoblastic lymphoma. Anaplastic lymphoma kinase protein expression in small round cell tumors of childhood is poorly described in the literature. The findings of our study highlight a potential and possible role of targeting ALK in pediatric solid tumors by using ALK immunohistochemistry. Anaplastic lymphoma kinase may also have an oncogenic role in rhabdomyosarcomas and peripheral neuroblastic tumors, and they may possibly be treated with ALK inhibitors. Anaplastic lymphoma kinase expression in Wilms tumors is not reported in the literature, previously. Our study evaluated ALK expression in Wilms tumor samples. (C) 2015 Elsevier Inc. All rights reserved.