• Typically patients in age 50s, M:F 1:1
• Most RP liposarcs are malignant (80%)
• Distant mets present in 10% of patients at presentation
• DDx for RP mass - lymphoma, metastatic testicular cancer/germ cell tumor; schwannomas and paraganglionomas; retroperitoneal fibrosis
• Histology - well-differentiated > de-differentiated >> myxoid, round cell, pleomorphic
  • Well-differentiated does not metastasize but will recur
  • De-differentiated can metastasize and high risk of recurrence
• Staging
  • T1 < 5 cm
  • T2 5-10 cm
  • T3 10-15 cm
  • T4 > 15 cm
• Grading
  • Differentiation score
    • 1 - low-grade
    • 2 - uncertain (e.g. myxoid, round cell)
    • 3 - undifferentiated
  • Mitotic count
    • 1 - 0-9 mitoses/HPF
    • 2 - 10-19
    • 3 - >= 20
  • Necrosis score
    • ​​​​​​​0 - no necrosis
    • 1 - < 50% necrosis
    • 2 - >= 50% necrosis
  • G1 total differentiation, mitotic count, and necrosis score 2-3
  • G2 4-5
  • G3 6-8

Clinical presentation

• Generally due to compression of adjacent structures (e.g. lower extremity edema, groin pain, early satiety)

• Basic labs, testicular tumor markers to see if might be testis cancer
• CT to evaluate relation to other organs
• Biopsy

Initial treatment

Surgery or surgery with neoadjuvant RT

• R1 (positive microscopic margins) accepable as 'complete resection' because very hard to achieve R0. R0/R1 managed with surveillance.
• R2 - lack of data to support adjuvant RT.

Metastatic or unresectable disease - anthracycline-based chemotherapy (e.g. doxycycline)