Introduction 1 2 Clinical symptoms vary widely, based on the location of the primary tumour, but in general presenting symptoms often are indolent, with nonspecific or minimal symptoms, at the start mimicking innocent general paediatric diseases. Often the duration or progression of symptoms alerts the physician to the presence of a malignant tumour. Site-specific symptoms in GU-NBP tumours are a paratesticular mass in boys that may be painful or not, while girls may present with a grape-like (botryoid) vaginal extrusion of mucosanguineous tissue or micturition problems. BP tumours may present with urinary retention, haematuria, constipation or an abdominal mass. Limb tumours often present with a painless swelling and/or with enlarged regional lymph nodes, while presentation of tumours in other locations may vary from biliary obstruction in tumours of the biliary tract, to painless masses, all depending on their primary site. 3 1 Table 1 28   Favourable Unfavourable Histology Embryonal Alveolar IRSG status Higher grades more unfavourable Tumour site Head and neck non-parameningeal All other sites Orbital Genitourinary – nonbladder/prostate Node involvement N0 N1 Tumour size (cm) ≤5 >5 Age (years) <10 ≥10 Pathology 4 5 1 2 Fig. 1 Embryonal RMS: small cells and primitive spindle-shaped cells resembling the first stages of developing normal skeletal muscle (H&E, original magnification 10×20)  Fig. 2 Embryonal RMS, spindle-cell type: closely packed spindle cells arranged in perpendicular crossing fascicles giving a leiomyosarcoma-like appearance (H&E, original magnification 10×20)  6 7 3 8 Fig. 3 Alveolar RMS: cluster of primitive cells with loss of cellular cohesion and bordered by dense fibrous septa, resulting in an alveolar pattern (H&E, original magnification 10×20)  9 10 4 11 Fig. 4 Sclerosing RMS: small cells, primitive spindle-shaped cells and eosinophilic rhabdomyoblasts in a background of hyaline sclerosis (H&E, original magnification 10×20)  2 12 Table 2 12 Group Prognosis Subtype I Better prognosis Embryonal RMS, botryoid type Embryonal RMS, spindle-cell type II Intermediate prognosis Embryonal RMS (remaining) III Worse prognosis Alveolar RMS IV Unclear prognosis RMS with rhabdoid features Embryonal RMS with diffuse anaplasia Sclerosing RMS Imaging findings Radiography As RMS is a soft-tissue tumour, conventional radiology plays an insignificant role in its diagnosis. Localized bony erosion adjacent to the primary site is a recognized complication; this area may be hot on a 99mTc-MDP bone scan in the absence of metastatic disease in the skeleton. In contrast to the initial diagnostic work-up, where for the assessment of pulmonary metastases CT is mandatory, AP and lateral chest radiographs are used in the follow-up period. Ultrasonography US is often the first imaging modality used in children with soft-tissue masses because it is readily available, has high resolution, and can easily assess extent and vascularity of a mass. One should not forget that most soft-tissue lesions are benign, can readily be diagnosed with US, and do not need further diagnostic work-up or even treatment. 5 Fig. 5 open arrow solid arrow  13 CT 3 14 15 14 15 MRI 16 6 6 7 Fig. 6 a arrow b arrow  Fig. 7 a open arrow solid arrow b open arrow  17 18 19 18 19 Bone scintigraphy In the current EpSSG protocols, bone scintigraphy is mandatory as part of the work-up in patients with RMS. The finding of an isolated hot spot on the bone scan should be evaluated with conventional radiography or MRI. 20 21 Positron emission tomography-CT 18 22 18 8 Fig. 8 18 open arrow solid arrows  23 24 Staging and follow-up Staging of RMS is of importance for the individual patient as it gives an indication of prognosis, and thus treatment stratification. From a broader perspective staging makes compiling data on larger patient groups for research purposes possible, enabling evaluation of the outcome of different treatment regimens. 3 25 P 7 26 Table 3 IRSG classification Stage Characteristics I Localized disease completely resected (regional nodes not involved) A: Tumour confined to muscle or organ of origin B: Tumour infiltrating outside organ of (muscle of) origin II Localized or regional disease with total resection of gross tumour A: Primary tumour grossly resected, with microscopic residual disease (negative findings in local nodes) B: Primary tumour and positive nodes completely resected C: Primary tumour and positive nodes resected, with evidence of microscopic residual disease III Incomplete resection of tumour or biopsy, with gross residual disease IV Distant metastatic disease present at diagnosis 4 3 27 Table 4 Regional node stations by primary tumour site. Disease with involvement of other lymph nodes than those specified in the table should be classified as stage IV Anatomical site Node station Extremity Lower extremity Inguinal, femoral, popliteal nodes (rare) Upper extremity Axillary, brachial, epitrochlear, and infraclavicular nodes Genitourinary Bladder, prostate, cervix, uterus, paratesticular Pelvic, retroperitoneal nodes at renal artery level or below Vagina Retroperitoneal, pelvic nodes at or below common iliac inguinal nodes  Vulva Inguinal nodes Thoracic Intrathoracic Internal mammary, mediastinal nodes Retroperitoneum/pelvis Pelvic, retroperitoneal nodes Trunk Abdominal wall Inguinal, femoral nodes Chest wall Axillary, internal mammary, and infraclavicular nodes Other Biliary Liver hilar nodes  Perianal/perineal Inguinal, pelvic nodes (may be bilateral) 1 28 28 29 30 31 32 9 33 Fig. 9 6 a open arrow b open arrow solid arrow c open arrow  Tumour locations Genitourinary 34 35 10 5 11 36 48 49 50 Fig. 10 open arrow  Fig. 11 a asterisk open arrow b  Extremities 12 13 51 52 53 Fig. 12 a open arrow b  Fig. 13 open arrow  Other Chest wall 14 54 55 57 57 Fig. 14 a asterisk b c  Pulmonary 58 62 63 15 64 65 Fig. 15 open arrow solid arrow asterisk  Biliary tree 66 16 16 16 67 Fig. 16 a open arrow solid arrow b open arrow c open arrow d  Other locations 17 68 76 Fig. 17 open arrow  Congenital 18 77 81 79 82 81 Fig. 18 a b open arrow  Adult patients 19 83 86 85 Fig. 19 A 45-year-old man with a mass in the thigh. T1-W contrast-enhanced MR image shows a heterogeneous circumscribed mass in the vastus lateralis muscle of the right leg. Histopathology: alveolar RMS  Differential diagnosis 20 21 Fig. 20 a b open arrow c open arrow  Fig. 21 open arrow  Treatment and prognosis Treatment of RMS requires a multidisciplinary approach, where chemotherapy, surgery and radiotherapy (RT) each has its own specific role. Chemotherapy 87 88 Surgery In children surgery often starts during the diagnostic phase with biopsy for histological studies, although here interventional radiology plays an increasing role. Excisional biopsy is not advocated except for paratesticular tumours. Most patients end up with postsurgical stage IRS group III. Surgery is generally delayed until after tumour reduction by chemotherapy. The surgical treatment of RMS is site-specific, but the current paradigm is complete wide excision of the primary tumour with a margin of uninvolved tissue whenever possible. Debulking and mutilating procedures should be avoided. Radiotherapy 89 90 91 92 European approach 93 98 93 99 100 93 93 North American approach 5 87 87 88 101 102 90 Table 5 28 Stage Site a b c d I Orbit T1 or T2 a or b N0, N1 or NX M0 Head and neck (excluding parameningeal) Genitourinary, nonbladder nonprostate II Bladder and prostate T1 or T2 a N0 or NX M0 Extremity Cranial parameningeal Other (including trunk, retroperitoneum, etc) III Bladder and prostate T1 or T2 a N1 M0 Extremity Cranial parameningeal T1 or T2 b N0, N1 or NX M0 Other (including trunk, retroperitoneum, etc) IV All sites T1 or T2 a or b N0 or N1 M1 a T1 T2 b a b c N0 N1 NX d M0 M1 90 Current EpSSG approach IRS group I 101 103 103 IRS group II 104 104 IRS group III 28 Prognosis 101 105 107 26 100 108 111 112 113 The postoperative patient 22 Haematoma Oedema Soft-tissue infection/abscess Calcification Foreign bodies Muscle flaps/fat pads Distorted anatomy Radiation effect 23 Fig. 22 asterisk open arrow solid arrow  Fig. 23 SI CE 114  Conclusion In this review we have discussed the findings of RMS outside the craniofacial region. The treatment of RMS requires a multidisciplinary approach, in which paediatric oncologists, radiologists, paediatric surgeons, pathologists and radiation oncologists all play a vital role. Although they are the most common soft-tissue tumour of childhood, these still rare tumours should be evaluated and treated in specialized centres.