Rhabdomyosarcoma Mimicking Otomastoiditis in a Preschool Child with Facial Paralysis.

Rhabdomyosarcoma of the temporal bone is an uncommon but important malignant mimic of pediatric otomastoiditis. We describe a 4-year-old boy who presented with persistent right-sided otorrhea after an upper respiratory tract infection, followed by an external auditory canal mass and progressive right peripheral facial nerve paralysis. Temporal bone computed tomography showed soft-tissue opacification of the right external auditory canal, tympanic cavity, mastoid antrum, and mastoid air cells. Magnetic resonance imaging demonstrated an irregular, heterogeneously enhancing lesion involving the same regions and adjacent to the expected course of the facial nerve canal. Initial imaging favored otomastoiditis with possible cholesteatoma. Biopsy revealed a malignant small round cell soft-tissue tumor infiltrating the subepithelial stroma. Immunohistochemistry showed desmin positivity and nuclear MyoD1 and myogenin positivity, supporting rhabdomyoblastic differentiation; embryonal rhabdomyosarcoma was favored. This case emphasizes that persistent pediatric otorrhea with an aural mass, blood-stained discharge, facial paralysis, or extensive temporal-bone soft tissue should prompt early imaging and biopsy to avoid diagnostic delay.