Liver & intrahepatic bile ducts

Benign / nonneoplastic

Mesenchymal hamartoma

Topic Completed: 1 February 2012

Minor changes: 11 June 2021

Copyright: 2002-2021,, Inc.

PubMed Search: Mesenchymal hamartoma[TI] liver[TI] full text[sb]

Deepali Jain, M.D.
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Cite this page: Jain D. Mesenchymal hamartoma. website. Accessed December 8th, 2021.
Definition / general
  • Well circumscribed, solitary myxoid mass with fluid filled cysts, with architecturally abnormal bile ducts in primitive myxoid stroma (Arch Pathol Lab Med 2006;130:1567)
  • Third most common tumor of liver in pediatric age group (after hepatoblastoma and infantile hemangioma)
  • Formerly called cavernous lymphangioadenomatoid tumor, cystic hamartoma, benign mesenchymoma
Clinical features
  • 8% of pediatric liver tumors
  • 75% < age 1 year; rarely adults; 60 - 70% male
  • Right lobe predilection
  • Usually asymptomatic
  • Serum AFP usually normal or mildly elevated; occasionally markedly elevated
  • Either neoplastic or a developmental anomaly in bile duct plate formation, possible hepatic stellate (Ito) cell origin (Pathol Res Pract 2010;206:532)
  • Rarely associated with undifferentiated embryonal sarcoma (Pediatr Dev Pathol 2001;4:482) - are pathogenetically related (Genes Chromosomes Cancer 2007;46:508)
  • Adult cases are usually women with abdominal pain, more prominent fibrosis and a lesser myxoid component than childhood cases, usually no extramedullary hematopoiesis (Hum Pathol 2002;33:893)
Case reports
  • Excision (curative but surgery has high mortality for large masses)
  • Liver transplantation may be necessary (J Clin Pathol 2006;59:542)
Gross description
  • Well circumscribed, solitary, 5 - 23 cm, 20% pedunculated, myxoid mass with fluid filled cysts
  • May be multiloculated
  • Becomes fibrotic with age
  • Cysts are variable sized, contain mucoid or pink fluid with adjacent solid, pink white areas
  • May have satellite nodules; usually no necrosis, hemorrhage or calcification
Gross images

Images hosted on other servers:

Well demarcated tumor with solid grey cut surface, slightly nodular appearance, isolated small hemorrhagic areas

Microscopic (histologic) description
  • Epithelial and mesenchymal components
  • Branching bile ducts without atypia in loose, myxoid stroma with myofibroblast-like cells, dilated vessels and lymphatics
  • May resemble breast fibroadenoma at low power
  • Also normal appearing hepatocytes with retention of normal cell plate architecture, thick walled veins, variable collagen
  • Bile ducts may have mesenchymal collars and are often cystically dilated
  • Usually extramedullary hematopoiesis (90%)
  • Often pools of fluid; no tumor giant cells
  • Adult cases have densely hyalinized or fibrotic stroma and only focal myxoid areas
Microscopic (histologic) images

Case #61

Various images

Negative stains
Electron microscopy description
  • Myofibroblastic features
Molecular / cytogenetics description
Differential diagnosis
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