Synonyms

• Embryonal rhabdomyosarcoma
• alveolar RMS
• pleomorphic RMS

Category

Soft tissue

Behaviour

Malignant

Grade

High

Gender

Both equally

Tissue of Origin

Skeletal muscle

Epidemiology

• Most common soft tissue sarcoma in children
• Peak incidence <5 years for embryonal subtype
• Alveolar: slightly older children

Clinical Features

• Rapidly growing mass
• Pain if deep location
• Site-dependent symptoms (biliary, bladder obstruction)

Location

• Biliary tract (botryoid)
• Bladder/prostate (botryoid)
• Extremities
• Head and neck
• Parameningeal locations

Imaging

• MRI primary site - essential for surgical planning
• CT chest/abdomen/pelvis - metastatic staging

Pathology

• Small round cells with myogenic differentiation
• Embryonal: myxoid background
• Alveolar: nested pattern with PAX-FOXO1 fusion

Genetics

• PAX3-FOXO1 in alveolar (t(2;13))
• PAX7-FOXO1 in alveolar (t(1;13))
• PAX-FOXO1 negative in embryonal

Treatment

• Multiagent chemotherapy (VAC/IE)
• Local control: surgery and/or radiotherapy

Prognosis

• Embryonal: 70% 5-year survival
• Alveolar: 50% 5-year survival
• Stage and histology critical prognostic factors

Key Points

• Most common soft tissue sarcoma in children
• PAX-FOXO1 status defines risk stratification
• Multimodal therapy standard

Workup - Blood Tests

• FBC, U&E, LFTs - baseline and pre-chemo
• LDH - prognostic marker

Workup - Local Imaging

• MRI primary site with gadolinium - local staging
• CT chest/abdomen/pelvis - metastatic staging
• PET-CT - systemic staging

Workup - Biopsy

• Core needle biopsy - confirm diagnosis
• PAX-FOXO1 FISH essential for prognostic stratification

Workup - Staging

• CT chest/abdomen/pelvis - metastases
• PET-CT - staging

Workup - Other

Paediatric oncology MDT mandatory

Follow-up Summary

• Year 1: 2-monthly clinical examination, CXR, plain films of primary bony site; soft tissue tumours - baseline end-of-treatment MRI/CT primary site, thereafter at clinician's discretion; radiotherapy as definitive local treatment - baseline end-of-treatment MRI/CT, then at 6 and 12 months; end of Year 1 - gonadal function and renal function
• Years 2–3: 3-monthly clinical examination, CXR, plain films of bony primary site; MRI of soft tissue primary site at clinician's discretion; radiotherapy patients - MRI/CT at 18 and 24 months; MUGA/ECHO 2 years post-diagnosis; annual renal function
• Year 4: 6-monthly clinical examination, CXR, plain films of primary site; MRI of soft tissue primary at clinician's discretion; MUGA/ECHO 4 years post-diagnosis; annual renal function
• Year 5: 6-monthly clinical examination, CXR, plain films of primary site; annual renal function
• Years 6–10: Annual clinical examination, CXR, plain films of primary site; MUGA/ECHO 6 years post-diagnosis; annual renal function
• Discharge at 10 years after surgery