Abstract
OBJECTIVE Mesenchymal hamartoma of the liver (MHL) Is a rare disease that makes up about 5%-8% of primitive hepatic tumors in children. The etiology of MHL has been the subject of considerable discussion. The possibility of malignant transformation of MHL is inclusive. To enhance the recognition of MHL in children, we have review the procedures in diagnosis and treatment and present 4 of our own cases.
METHODS The clinical characteristics of MHL in 4 children including history, physical examination, lab examination, imaging data and pathology were analyzed and discussed and related to reports from the literature.
RESULTS All the cases were diagnosed with B-ultrasonography and CT preoperatively, and were confirmed intra-operatively and histologically. Satisfactory results were reached postoperatively.
CONCLUSION MHL is an uncommon benign lesion in children. The main presentation is abdominal painless mass. Diagnosis is aided with B-ultrasonography and CT preoperatively. Complete tumor removal is the best choice for MHL treatment resulting in a good outcome.
keywords
Mesenchymal hamartoma of the liver (MHL) is an uncommon, hepatic mass lesion that occurs primarily in children with most MHL occurring in the right lobe of the liver. MHL is a pedunculate tumor, rising from the inferior liver surface and is often large in size with solid components inside. With tumor growth, it will form multiple cysts. The majority of cases are diagnosed at or before 2 years of age with presentation of an abdominal mass or enlarged abdomen. [1,2,3] Biochemical liver function tests are usually normal. With ultrasound, CT and MRI, the tumors demonstrate a multiloculated cystic tumor with a variable amount of solid tissue. Fine-needle aspiration cytology is also a tool for diagnosis. The etiology of MHL has been the subject of considerable discussion.[4,5,6] and the possibility of malignant transformation of MHL is inclusive.[7] Hepatic lobectomy is a major operation, which is feasible yielding curative results in children. In this report, we described 4 cases of MHL in children and review the procedures for diagnosis and treatment.
MATERIALS AND METHODS
There were 2 female and 2 male cases, 8 to 37 months of age. The average age was 21 months Typically they grew to a large tumor mass with minimal symptoms. There were no typical clinical signs. Preoperation examination included: AFP was negative and liver function tests including serum ALT, AST, ALP were normal. Ultrasond (4 cases), CT (3 cases) and MRI (2 cases) were conducted. The radiographic characteristics of the MHL were multicystic or solid cystic tumor in the liver. Three of the 4 tumors were located in the right lobe of the liver and 2 of the tumors were large in diameter. The procedures employed included local resections (3 cases), and nucleated resection (1 case) Table 1.
The clinical data of mesenchymal hamartoma of the liver
RESULTS
A recurrence only occurred for case 2. The size of the tumor in case 3 gradually reduced without accompanying symptoms. Follow-up time lasted from 7 months to 6 years Table 2.
The follow-up results
DISCUSSION
Epidemiology
MHL is a rare disease that makes up about 5%~8% of primitive hepatic tumors in children. The tumor is slightly more common in boys. It is a benign lesion that presents mostly before the age of 2 years reported as nationally ni and 1 year internationally.[2,3] MHL has been rarely reported in the prenatal period18-121 or adulthood.[13,14,15,16]
Etiology
The etiology of MHL has been the subject of considerable discussion and only recently has converged around some degree of consensus. These lesions traditionally have been considered as developmental abnormalities related to other bile duct plate malformations including bile duct hamartomas, Caroli’s disease, or the hepatic cysts associated with polycystic kidney disease. The presence of satellite lesions in cases of MHL, consisting of malformed portal triads with irregular, branching bile ducts, is suggestive of a relationship to these developmental processes. MHL has been showed to have chromosomal translocations involving 19ql3.4. Several cases of undifferentiated embryonal sarcoma are also known to contain such translocations, further supporting that MHL may represent a true neoplasm. [4,5,6]
Clinical characteristics
MHL may be found incidentally on physical examination or imaging, but typically it presents with abdominal distension and/or an upper abdominal mass.[17-19] Our four cases presented with an upper abdominal mass (3 cases) and abdominal distension (1 case). The tumor can cause respiratory distress, apnea or obstructive jaundice. It sometimes will induce failure of liver function, even death due to hepatic coma.[20] Typically, examination reveals a large, non-tender, firm, and smooth liver tumor.
Laboratory and image analyses
Biochemical liver function tests are usually normal. In some patients the serum AFP concentration is moderately elevated.[21] But our data showed that both biochemical liver function tests and AFP concentration were normal.
Ultrasound demonstrates (US) that MHL is a multi-loculated cystic tumor with a variable amount of solid tissue. Cysts are frequently septated, but rarely contain debris. With US, the outer rim of compressed liver and the hepatic architecture appear normal Fig. 1.
Case 3: Ultrasound demonstrated that the mass was a multiloculated cystic tumor with a variable amount of solid tissue.
Computed tomography (CT):[21] Most cass of MHL appear with a low intensity and are hypovascular on imaging. Solid areas, septae, and peripheral regions may enhance after intravenous contrast; delayed images may show persistent peripheral and septal enhancement with centripetal fill-in of solid areas Fig. 2.Magnetic resonance imaging (MRI): 122-241 typically, tumors have a low signal intensity on T1-weighted magnetic resonance sequences, but a variable signal intensity on T2-weighted sequences Fig. 3.
Case3: CT scanning showed a low-density and hypovascular.
Case 3: MRI demonstrated that the tumor had a low signal intensity on T1 -weighted magnetic resonance sequences.
Pathologic characteristics
Most of the MHL occur in the right lobe of the liver and 3 of our 4 csaes occured there. MHL is a pedunculate tumor, rising from the inferior surface of the liver and is often large size with solid components inside. With the tumor growth, it will form multiple cysts. A cut section will show there are multiple cysts containing clear or pale yellow serous fluid or mucoid material. The lesions are well circumscribed with a sharp margin between the mass and the surrounding, grossly unremarkable hepatic parenchyma.
Histological sections in each case show that the tumor is rich in mature connective tissue with considerable much deformation of blood vessels, lymphatic vessels and disorder of the small bile duct and its branchs. The tumor with mainly solid tissue contains fatty adipose, smooth muscle and osteoid tissue. The tumor with mainly cystic tissue includes multiple cysts containing clear or pale yellow serous fluid, partly cystic wall lining by flat mésothélial cells, circumscribed with blood vessels. The small bile ducts, lymphatic vessels and disorder of the small bile ducts and its branchs incased in a mass of hepatocyte. Hepatocytes around the tumor form irregullur mesenchymal tissue. The small bile duct and small cysts often weave together complicatedly. The origin of MHL, it is often from mesoderm, not from endoderm. For case 3, only bile ducts, smooth muscle, and fatty tissue were seen but no hepatic tissue was found. Based on the composition, some authors divide MHL into 2 groups: one from endoderm, another from mesoderm. MHL sometimes is accompanied with other malformations.[25,26]
Jmmrmohistology
The mesenchymal components of the tumor may be immunoreactive to vimentin and smooth muscle actin. Flow cytometry studies have shown that most MHLs are diploid but some are aneuploid indicating that it is real tumor. Bcl-2 overexpression and a very low apoptotic index suggests the MHLs grow slowly [18] Fig. 4.
Histological section showing that the tumor is rich in mature connective tissue, and there is significant deformation of blood vessels, lymphatic vessels and disorder of small bile duct and its branchs (x 100).
Diagnosis and differentiation
Although we believe that the diagnosis of the MHL is not difficult, the final diagnosis depends on pathologic results. The diagnostic characteristics of MHL:[28] it of-ten occurs in children under 2 years old. Most of them are admitted because of enlargement of the abdominal perimeter. Ultrasound, CT, MRI demonstrates a multi-loculated cystic tumor with a variable amount of solid tissue. Fine needle aspiration cytology is also a tool for diagnosis. The differential diagnosis of MHL is below: [28] undifferentiated embryonal sarcoma, hepatoblastoma, lymphangioma, hepatic cyst, hemangioma and Caroli’s diseas.
Therapy and prognosis
We regard that treatment of choice to be surgical resection, although the large size of the lesion and the involvement of vital structures may sometime result in incomplete excision.[29,30,31] Although most of doctors deem that the possibility of malignant transformation of MHL does not occur, some authors indicate through their studies that these lesions may undergo malignant transformation.[7] From our data, we have not found any malignant transformation cases. Recently some authors have reported nonoperative management of the asymptomatic mass,[32] but the prognosis was waiting for conformation. Over all, MHL has a good prognosis. Complete excision is the key for no recurrence.
- Received July 4, 2006.
- Accepted August 14, 2006.
- Copyright © 2006 by Tianjin Medical University Cancer Institute & Hospital and Springer
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