Purpose or Case Report: Paediatric soft-tissue sarcomas encompass a diverse group of malignant mesenchymal tumours with overlapping imaging features. Although differing in molecular background, these tumours often appear radiologically similar, posing diagnostic challenges even to experienced radiologists. Rhabdomyosarcoma, the most frequent subtype, illustrates the broad radiologic spectrum of these lesions.
Radiologic evaluation is pivotal—not only for staging and therapy planning, but also for distinguishing viable tumour from post-treatment fibrosis or benign mimics. MRI remains the cornerstone of assessment, providing superior soft-tissue contrast and functional information through diffusion-weighted and contrast-enhanced sequences, which improve the detection of subtle tumour viability and therapy response.

Rhabdomyosarcomas usually manifest as heterogeneous soft-tissue masses that are isointense to muscle on T1 and hyperintense on T2-weighted imaging, reflecting variable amounts of necrosis, haemorrhage, and myxoid stroma. Embryonal rhabdomyosarcoma, the most frequent subtype, predominates in younger children and typically arises in the head and neck, genitourinary tract, or biliary system. It appears as an ill-defined, infiltrative mass with heterogeneous enhancement and restricted diffusion in solid components. The botryoid subtype, a variant of the embryonal form, develops in mucosa-lined cavities such as the biliary tree, bladder, or vagina, presenting as a grape-like polypoid intraluminal mass often causing luminal or ductal dilatation. Alveolar rhabdomyosarcoma, more frequent in adolescents and in the extremities or trunk, tends to be better defined, sometimes producing osseous erosion or fascial invasion, and often demonstrates more pronounced diffusion restriction due to its higher cellularity. These anatomic and morphologic distinctions provide essential clues for biopsy targeting, staging, and multidisciplinary planning.

By integrating current literature and representative institutional cases, this poster offers a focused visual guide to the MRI hallmarks and interpretative challenges of paediatric rhabdomyosarcoma, highlighting the radiologist’s role in tumour characterisation and multidisciplinary care.
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