Unusual case of inflammatory rhabdomyoblastic tumor in a pediatric patient

Inflammatory rhabdomyoblastic tumor (IRMT) is a rare, recently described skeletal muscle neoplasm of uncertain malignant potential. We report an unusual tumor in the right arm of a 5-year-old boy, which is the first case of a pediatric IRMT. Immunohistochemically, most cells in the tumor were positive for CD163 and CD68 staining. The neoplastic cells themselves showed a skeletal muscle phenotype with a diffuse expression of desmin and a focal expression of myoD1. Mitotic activity was low (1/10 HPF), and no necrosis was observed.