Alveolar Rhabdomyosarcoma
Synonyms: ARMS, alveolar-type rhabdomyosarcoma
Highly aggressive rhabdomyosarcoma characterized by primitive, round cells showing skeletal muscle differentiation
Quick Facts
Behaviour
Malignant
Category
Soft tissue
Grade
High
Synonyms
- ARMS
- alveolar-type rhabdomyosarcoma
Category
Soft tissue
Behaviour
Malignant
Grade
High
Gender
M = F
Tissue of Origin
Skeletal muscle
Epidemiology
- High-grade embryonal rhabdomyosarcoma subtype
- Peak incidence in older children than embryonal rhabdomyosarcoma
- Peak incidence 10-25 years
- More aggressive than embryonal type
Clinical Features
- Rapidly growing deep soft tissue mass
- Metastases often present at diagnosis (25-30%) via lymphatic or hematogenous spread
Location
- Extremities most common
- Trunk and paraspinal region
- Head and neck
Imaging
- Radiological features are nonspecific in differentiating from other sarcomas
- Plain radiograph: soft tissue density mass
- Ultrasound: heterogeneous non uniform mass of low to medium echogenicity
- CT: soft tissue density lesion with contrast enhancement
- MRI: low to medium intensity lesion on T1, hyperintense lesion with conspicuous vascularity on T2
Pathology
- Nested architecture with PAX-FOXO1 fusion
- Small round cells with myogenic features
- Higher grade than embryonal type
Genetics
PAX3-FOXO1 (t(2;13)) or PAX7-FOXO1 (t(1;13)) translocations
Treatment
- Intensive multiagent chemotherapy based on risk group
- Wide local resection for local control and/or radiotherapy
- Radiotherapy to primary tumour and metastatic sites may be considered
- Intergroup Rhabdomyosarcoma Study Postsurgical Clinical Grouping System is recommended to plan treatment
Prognosis
- 50% 5-year survival for alveolar subtype
- Fusion-positive ARMS has worse prognosis
- Metastatic disease at diagnosis significantly impacts prognosis
Key Points
- Highly aggressive rhabdomyosarcoma characterized by primitive, round cells showing skeletal muscle differentiation
- Older age of presentation than embryonal type
- Higher metastatic potential
Workup - Blood Tests
- FBC, U&E, LFTs - baseline and pre-chemo
- LDH - prognostic marker
Workup - Local Imaging
MRI with contrast of primary site
Workup - Biopsy
- Core needle biopsy
- Lymph node biopsy if lymph node involvement is clinically or radiologically doubtful, and as standard of care in extremity RMS
- Molecular workup - minimum evaluation of FOX01 fusion status and MY0D1
Workup - Staging
- CT chest/abdomen/pelvis
- Whole body MRI or PET-CT per LSESN guidelines
Workup - Other
Paediatric oncology MDT mandatory
Follow-up Summary
Medical disclaimer
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