MalignantBone
Small Cell Osteosarcoma
Synonyms: Juvenile OS variant, small cell OS
Small cell variant but aggressive like conventional OS
Quick Facts
Behaviour
Malignant
Category
Bone
Grade
High
Synonyms
- Juvenile OS variant
- small cell OS
Category
Bone
Behaviour
Malignant
Grade
High
Gender
M = F
Tissue of Origin
Bone
Epidemiology
- Rare small cell variant of osteosarcoma
- Similar age incidence to conventional OS
- Lower extremity predominance
Clinical Features
- Pain and swelling
- Rapid progression
Location
- Distal femur
- Proximal tibia
- Same sites as conventional OS
Imaging
- Radiograph: aggressive lytic/sclerotic lesion
- MRI: local staging
- CT chest: pulmonary staging
Pathology
- Small round cell sarcoma with focal osteoid production
- Can be misdiagnosed as Ewing sarcoma
- Osteoid is diagnostic feature
Genetics
- TP53, RB1 alterations
- Complex karyotype
Treatment
- MAP chemotherapy same as conventional OS
- Wide surgical resection
- Local control with surgery/radiotherapy
Prognosis
- Similar to conventional OS with modern chemotherapy
- 60-70% 5-year survival
Key Points
- Small cell variant but aggressive like conventional OS
- Osteoid production distinguishes from Ewing
- Treated identically to conventional OS
Workup - Blood Tests
- FBC, U&E, LFTs, Bone profile
- Alkaline phosphatase, LDH
Workup - Local Imaging
- Plain radiograph, MRI primary site
- CT chest, Bone scan/whole-body MRI
Workup - Biopsy
Core needle biopsy with osteoid identification critical
Workup - Staging
CT chest, skeletal staging
Medical disclaimer
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