Atypical Lipomatous Tumour
Synonyms: Well-differentiated liposarcoma (retroperitoneal), ALT
MDM2 amplification is the key diagnostic marker
Quick Facts
Behaviour
Intermediate
Category
Soft tissue
Synonyms
- Well-differentiated liposarcoma (retroperitoneal)
- ALT
Category
Soft tissue
Behaviour
Intermediate
Gender
Male
Tissue of Origin
Adipose
Epidemiology
- Most common liposarcoma subtype
- Peak incidence 50-70 years
- Most common malignant soft tissue tumour in adults
Clinical Features
- Large, slow-growing, deep soft tissue mass
- Often painless
- May be very large at presentation (>10cm)
- Retroperitoneal location may cause mass effect symptoms
Location
- Deep soft tissue of extremities (especially thigh)
- Retroperitoneum
- Paratesticular region
- Mediastinum
Imaging
- MRI: predominantly fat signal with thick septa (>2mm)
- Enhancing non-lipomatous components
- CT: fat-density mass with soft tissue stranding
- Differentiate from benign lipoma by size, depth, septa
Pathology
- Mature adipocytes with scattered atypical stromal cells
- Lipoblasts may or may not be present
- Fibrous septa with atypical hyperchromatic cells
- MDM2 and CDK4 amplification on FISH/IHC
Genetics
- MDM2 amplification (chromosome 12q13-15) is diagnostic marker
- FISH for MDM2 is gold standard confirmatory test
Treatment
- Wide surgical excision
- Marginal excision acceptable in extremity (ALT) with close follow-up
- Retroperitoneal WD liposarcoma: complete resection is critical
- No role for adjuvant chemotherapy or radiotherapy in most cases
Prognosis
- Extremity ALT: no metastatic potential, but local recurrence risk
- Retroperitoneal WD liposarcoma: risk of dedifferentiation and recurrence
- Dedifferentiation rate 15-20% in retroperitoneal location
- Long-term follow-up essential (late recurrences)
Key Points
- MDM2 amplification is the key diagnostic marker
- Extremity ALT has no metastatic potential (but can recur locally)
- Retroperitoneal location has significantly worse prognosis
- Terminology: ALT in extremity, WD liposarcoma in retroperitoneum
Workup - Blood Tests
- FBC, U&E, LFTs - pre-operative baseline
- No specific tumour markers required
Workup - Local Imaging
- MRI primary site
- CT - useful for retroperitoneal lesions; fat attenuation with thick internal septa
Workup - Biopsy
Core needle biopsy - confirm diagnosis and exclude dedifferentiation before definitive surgery
Workup - Staging
- No routine metastatic staging required - ALT does not metastasise
- Staging imaging for retroperitoneal location to assess organ involvement
Workup - Other
- MDT review at soft tissue sarcoma specialist centre
- Document surgical margins - R0 reduces dedifferentiation risk in retroperitoneal ALT
Follow-up Summary
Soft Tissue Tumours - Localised Extremity - Benign / Atypical Lipomatous
Retroperitoneal tumours require long term follow up due to risk of dedifferentiation
Medical disclaimer
The content on Sarcopedia is for educational and informational purposes only and does not constitute medical advice. It is not intended to be a substitute for professional medical diagnosis or treatment. Always consult with a qualified physician regarding any health concerns or before starting any new treatment. Reliance on any information provided on this site is solely at your own risk.