Liver & intrahepatic bile ducts
Benign / nonneoplastic
Mesenchymal hamartoma
Author: Deepali Jain, M.D.
Topic Completed: 1 February 2012
Minor changes: 23 September 2020
Copyright: 2002-2021, PathologyOutlines.com, Inc.
PubMed Search: Mesenchymal hamartoma[TI] liver[TI] full text[sb]
Table of Contents
Definition / general | Clinical features | Case reports | Treatment | Gross description | Gross images | Microscopic (histologic) description | Microscopic (histologic) images | Positive stains | Negative stains | Electron microscopy description | Molecular / cytogenetics description | Differential diagnosisCite this page: Jain D. Mesenchymal hamartoma. PathologyOutlines.com website. https://www.pathologyoutlines.com/topic/livertumormesenchymalhamart.html. Accessed January 22nd, 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
- 10 month old girl with cytogenetic analysis (Arch Pathol Lab Med 2006;130:1216)
- 15 month old asymptomatic boy with large hepatic mass (Case of the Week #61)
Treatment
- 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
Positive stains
Negative stains
Electron microscopy description
- Myofibroblastic features
Molecular / cytogenetics description
- Interstitial deletion near 19q13.4 (Cancer Genet Cytogenet 2004;153:60)
Differential diagnosis
- Bile duct adenoma (no hepatocyte islands) or cystadenoma (adults)
- Bile duct hamartoma: usually multiple with fibrous background
- Embryonal sarcoma: marked cellularity and atypical cells, eosinophilic PASD globules
- Infantile hemangioendothelioma: more vascular
- Infantile hemangioma: females more common, vascular channels of variable size
- Mixed epithelial mesenchymal hepatoblastoma: epithelial component has embryonal and fetal hepatocytes; mesenchymal component has spindle cells, osteoid, cartilage
