LEC 4 soft tissue tumours

• Macroscopic (Gross) Findings of lipoma:

  • Well circumscribed
  • Large mass with a round-oval shape
  • Yellow-white, lobulated surface
  • Not encapsulated
  • Haemorrhagic spots
• Complications of lipoma:

  • Rare transformation into liposarcoma
• LIPOSARCOMA:
• Aetiology of liposarcoma:

  • Amplification of chromosome region 12q13-ql5, including MDM2 gene
  • MDM2 gene encodes a potent inhibitor of p53
  • t(12;16) resultant in a fusion gene that arrests adipose differentiation
• Risk factors for lipoma:

  • More common in adults, especially between ages 40 to 60
  • Some cases may have a genetic predisposition or familial tendency
  • Slightly more common in men than in women
  • Associated with conditions such as Gardner syndrome and adiposis dolorosa
• Clinical manifestations of lipoma:

  • Well circumscribed
  • Mobile
  • Solitary lesion
  • Painless
• Microscopic Findings of lipoma:

  • Thin capsule
  • Underlying lobules of mature adipose cells separated by delicate fibrous septa
  • Adipocytes with small nuclei
  • Well-defined edge
  • Sheets of uniform mature adipocytes
  • No atypia
  • Cytoplasm with eccentric nuclei
• Risk factors for liposarcoma:

  • Amplification of chromosome region 12q13-q15, including the MDM2 gene
  • Presence of t(12;16) resulting in a fusion gene that arrests adipose differentiation
• Pathogenesis of liposarcoma:

  • Amplification of chromosome region 12q13-q15, including the MDM2 gene
  • MDM2 gene encodes a potent inhibitor of p53
  • Presence of t(12;16) resulting in a fusion gene that arrests adipose differentiation
  • Complex karyotypes
• Clinical manifestations of liposarcoma:

  • Lump/mass in deep tissues of lower extremities, intermuscular regions in the thigh, buttocks, and retroperitoneum
  • Frequently recur locally when not adequately excised
  • Slow growing, aggressive, and metastasizes
• Complications of liposarcoma:

  • Depend on the histological type
  • Frequently recur locally when not adequately excised
  • May be slow growing, aggressive, and metastasizes
• RHABDOMYOSARCOMA:
• Morphology of rhabdomyosarcoma:

  • Densely-packed, primitive, small, round to oval cells with hyperchromatic nuclei and scant cytoplasm
  • Diagnostic cell is the rhabdomyoblast, round or elongated with granular, stringy, eosinophilic cytoplasm rich in thick and thin filaments
• Clinical manifestations of rhabdomyosarcoma:

  • Lump or mass in deep tissues of lower extremities, intermuscular regions in the thigh, buttocks, and retroperitoneum
  • Complications may include frequent local recurrence if not adequately excised
  • Aggressiveness and metastatic potential depend on the histological type, may exhibit slow growth and aggressive behavior leading to metastasis