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
• CDK4 co-amplification
• FISH for MDM2 is gold standard confirmatory test
• Ring and giant marker chromosomes

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
• Immunohistochemistry: MDM2+, CDK4+ on non-Adipose component
• MDM2 FISH - amplification confirms ALT/WD liposarcoma; essential for diagnosis

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

• Extremity:
• Year 1: Post-operative visit within first 6 weeks, then supported discharge
• Retroperitoneal:
• Year 1: Post-operative visit within first 6 weeks; 3–6 monthly clinical examination; baseline CT chest/abdomen/pelvis post-surgery, then at 6 and 12 months
• Year 2: 6-monthly clinical examination; CT chest/abdomen/pelvis at 18 and 24 months
• Year 3+: Annual clinical examination; annual CT chest/abdomen/pelvis to 10 years
• Discharge at 10 years after surgery