Abstract
Extraskeletal myxoid chondrosarcoma is an aggressive tumor in children. Due to its low incidence and nonspecific clinical presentation, as well as its radiological and histopathological characteristics, it is considered a diagnostic challenge. Furthermore, despite the NR4A3 rearrangement being specific to this neoplasm, its evaluation is not routinely performed, as few places have the technology to characterize it. We present the case of a 12-year-old girl with extraskeletal myxoid chondrosarcoma in the right thigh associated with lung metastasis. The diagnosis was ultimately made by integrating the clinical, radiological, histopathological, and ultrastructural features of the chondroblastic differentiation.