Mesenchymal hamartoma

Clinical features

• 8% of paediatric liver tumours
• 75% in patients less than one year of age
• 10-20% present at birth
• 75% in the right liver lobe
• Abdominal mass
• Benign
• Association with placental anomalies
• Most cases have no association with malformations

Cytopathology

• Monotonous population of spindle cells in clusters
• Pointed-end fusiform nuclei
• Myxoid proteinaceous background may be present

Immunocytochemistry

• Vimentin: positive

Genetic studies

• Breakpoint on chromosome 19

Differential diagnosis

• Hemangioendothelioma
  • Typically occurs before six months of age
• Inflammatory pseudotumor
  • Mesenchymal hamartoma is generally devoided of the inflammatory polymorphic population that characterizes inflammatory pseudotumor. However, rare cases of mesenchymal hamartoma may have extra medullary haematopoiesis, thus creating confusion
• Embryonal sarcoma
  • Highly aggressive appearance in smears: mitosis, necrosis and cellular pleomorphism
  • Hyaline globules
• Hepatic smooth muscle tumours (leiomyoma’s and leiomyosarcomas)
  • Rare cases have been described associated with HIV in children
  • Smooth muscle actin: positive

Main points

• Excision is curative but with high morbidity