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California Tumor Tissue Registry’s
Case of the Month
CTTR COTM www.cttr.org Vol 9:9
June, 2007
A two month old baby girl with a palpable abdominal mass was shown by ultrasound to
have a 4.7 x 3.2 cm pedunculated solid mass involving the inferior aspect of the liver
(Fig. 1). Chemistries were normal except for an elevated alpha-fetoprotein level of 2000.
A heterogeneous mass was resected (Fig. 2).
Microscopic sections showed a central zone of edematous loose connective tissue with
fibrin deposition and focal necrosis (Fig. 3, left). Surrounding were regions of variably
denser fibrous tissue with moderate prominence of thin-walled vessels and occasional
regions of hematopoiesis. Foci of aberrant small to mid-size blood vessels and foci of
dystrophic calcification were seen (Fig. 3, right). At the periphery, the lesion showed
variably edematous fibrous tissue with intermixed compressed hepatocytes, proliferating
bile ducts and ectatic vessels (Figs 4,5).
Diagnosis: “Hepatic Mesenchymal Hamartoma”
Wafaa Elatre, M.D., Fouad Abdelhalim, M.D., Craig Zuppan, M.D., Donald R.
Chase, M.D,
Department of Pathology, Loma Linda University and Medical Center
California Tumor Tissue Registry
Hepatic mesenchymal hamartoma (HMH) is a benign tumor-like process that usually
occurs in infancy or early childhood. Although the mean age is 16 months, cases have
occurred in children up to 5 years of age. The origin is mostly within the right lobe of the
liver. Most of the cases are asymptomatic and found incidentally, but some present with
a right upper quadrant mass, respiratory distress or fever. Liver function tests are usually
normal. Ultrasonography and computerized tomography may show an elevated
hemidiaphragm. A CT scan usually characterizes the mass as being complex with areas
of low attenuation separated by solid septae and stroma enhancing with intravenous
contrast. The etiology is uncertain, but a local vascular disturbance is suspected, at least
in some cases.
The differential diagnoses of benign childhood hepatic tumors are generally divided into
those of epithelial derivation (simple cysts, focal nodular hyperplasias and adenomas) and
those of mesenchymal derivation (usually hamartomas or hemangiomas). Mesenchymal
processes outnumber their epithelial counterparts and are briefly discussed below.
HMH is characterized by marked overgrowth by connective tissue of varying maturity
with a marked tendency to form cysts. The cysts are generally without a distinct lining
CTTR’s Case of the Month
June, 2007
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but in older children may have an attenuated epithelial lining. Cysts range from
microscopic to as large as 15 cm, and have a tendency to be larger in older children.
Although the mesenchyme may contain remnants of liver cells, duct cells and even portal
tissue, the most characteristic feature is the overgrowth of connective tissue. Lobular
architecture is maintained in any normal liver tissue at the periphery of the lesion.
Vascular lesions in the differential include infantile hemangioendothelioma and
cavernous hemangioma. On CT scan, these tumors are hypodense well-defined
homogenous masses sometimes with calcification.

Infantile hemangioendothelioma usually presents before six months of age and is
more common in females. It may be asymptomatic or present as hepatomegaly,
an abdominal mass or as high output cardiac failure. Microscopically the tumor
consists of variably sized vascular spaces lined by relatively immature plump
endothelial cells.

Cavernous hemangioma occurs in all age groups and is often asymptomatic and
discovered incidentally. It is usually a solitary lesion with a predilection for the
right lobe. It occurs more commonly in females. It consists of multiple dilated
blood filled spaces lined by mature flat endothelium and separated by fibrous
stroma.
With predominantly cystic lesions, the differential diagnosis also includes simple nonparasitic cysts and polycystic liver disease.

Simple cysts may be large and have a lining of columnar, cuboidal or flattened
epithelium. The wall is generally thin and composed of mature connective tissue
and may be calcified.

Polycystic liver disease is frequently associated with polycystic renal disease
(50%) and/or cystic processes involving the spleen, pancreas, ovaries and/or
lungs. Hepatic function is usually normal.
For predominantly solid lesions, the clinical differential diagnosis includes primarily
hepatoblastoma, which should be readily distinguishable under the microscope by its
malignant features and recapitulation of fetal or embryonal hepatocytes.
HMH generally carries an excellent long term prognosis. Treatment is surgical with four
options including enucleation, marsupialization of cysts, excision of hamartoma with
surrounding rim of normal liver tissue and formal hepatic lobectomy. Generally, excision
or marsupialization is recommended in most patients because of low morbidity and
mortality.
Suggested Reading:
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June, 2007
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1. Srouji MN, Chatten J, Schulman WM, Ziegler MM, Koop EC. Mesenchymal
hamartoma of the liver in infants. Cancer 42:2484-2489, 1978.
2. De Maioribus CA, Lally KP, Kenneth S, Hart H, Hossein M. Mesenchymal
hamartomas of the liver. A 35-years Review. Arch Surg; 125:598-600, 1990.
3. Ros PR, Goodman ZD, Ishak KG, Dachman AH, Olmsted WW, Hartman DS, et al.
Mesenchymal hamartoma of the liver: Radiologic - Pathologic correlation.
Radiol 158:619-625, 1986.
4. Dooley JS, Li AKC, Scheuer PJ, Hobbs KEF, Sherlock S. A giant cystic mesenchymal
hamartoma of the liver. Diagnosis, management and study of cyst fluid.
Gastroent. 85:958-961, 1983.
5. Suri S. Hepatic masses in children. In: Diagnostic Radiology: Pediatric Radiology,
New Delhi, 1st ed. Eds. Berry M, Suri S, Chowdhury V. Jaypee Brothers.
Medical Publishers limited, pp 42-51, 1997.
6. Johnston PW. Congenital cysts of the liver in infancy and childhood. Am J Surg; 116:
184-191, 1968.
7. Comfort MW, Gray HK, Dahlin DC, Whitesell FB. Polycystic disease of the liver: A
study of 24 cases. Gastroent 20:60-78, 1958.
8. Sherlock S, Dooley J. Cysts and congenital biliary abnormalities. In: Diseases of Liver
and Biliary System, 10th ed. Oxford, Blackwell Science, pp 579-591, 1997.
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