AJR 2004; 182:1214-1216
© American Roentgen Ray Society
Recurrent Hepatoblastoma in Orthotopic Transplanted Liver: Detection with FDG Positron Emission Tomography
S. Sironi1,2,
C. Messa1,2,3,
A. Cistaro3,
C. Landoni1,3,
M. Provenzi4,
E. Giraldi4,
A. Sonzogni5 and
F. Fazio1,2,3
1 School of Medicine, University of Milano-Bicocca, Milan, Italy.
2 IBFM-CNR Institute for Molecular Bioimaging and Physiology, Milan,
Italy.
3 Department of Nuclear Medicine, Scientific Institute H S. Raffaele, Via
Olgettina 60, Milan 20132, Italy.
4 Department of Pediatric Oncology/Haematology, Ospedali Riuniti, Bergamo,
Italy.
5 Department of Pathology, Liver Unit, Ospedali Riuniti, Bergamo, Italy.
Received July 23, 2003;
accepted after revision September 16, 2003.
Address correspondence to F. Fazio
(fazio.ferruccio{at}hsr.it).
Introduction
Hepatoblastoma is the most common malignant hepatic tumor in children, with
an annual rate of 1.3 cases per million. It is usually found during the first
3 years of life, and most patients are younger than 2 years. The term
"hepatoblastoma" indicates a group of tumors of embryonal origin,
histologically distinct from hepatocellular carcinoma of childhood
[1]. The clinical presentation
of hepatoblastoma is usually characterized by an abdominal mass and an
elevated level of serum 
-fetoprotein. Prognosis is poor when the tumor
is unresectable; however, complete resection is possible in about 50% of cases
[2]. Chemotherapy may produce
response in a significant number of patients, and preoperative chemotherapy
has been used with some success in converting unresectable tumors to
resectable. In children with an unresectable mass that is not responsive to
chemotherapy, orthotopic liver transplantation should be considered
[2]. Morphologic imaging
techniques such as CT, sonography, and MRI may locate a neoplastic liver mass;
but negative findings on conventional imaging studies do not always exclude
the presence of disease
[3–8].
Because, to our knowledge, the potential role of FDG positron emission
tomography (PET) in children with hepatoblastoma has not been previously
investigated, we report a case of a 4-year-old boy with orthotopic liver
transplantation as a result of hepatoblastoma, in whom tumor recurrence was
assessed with FDG PET.
Case Report
A 4-year-old boy with a history of fever, abdominal pain, and
hepatosplenomegaly underwent abdominal sonographic and liver CT examinations
that revealed multiple liver lesions with a maximum diameter of 4.5–5.5
cm (Fig. 1A). His serum
-fetoprotein level was 2,333 ng/mL. Hepatic biopsy was performed under
sonographic guidance, and the diagnosis of hepatoblastoma was made. At
histologic examination, the tumor was classified as the mixed
(mesenchymal–epithelial) type: 25% embryonal, 25% fetal, and 50%
trabecular hepatocellular carcinoma cells. Chemotherapy treatment was started
(four cycles of cisplatin, vincristine), but the tumor did not respond. This
fact, along with the absence of distant metastases on whole-body CT, suggested
liver transplantation as a possible therapeutic option.
The patient underwent surgical resection en bloc of the native liver and
received a segmental liver transplant (lateral segment of the left lobe). The
serum -fetoprotein level after transplantation was 188 ng/mL; however,
3 months later the serum -fetoprotein level increased to 1,248 ng/mL.
Contrast-enhanced CT of the transplanted liver was performed: no lesion was
seen in the liver parenchyma, but an irregular area of hypoattenuation was
noted along the posterior edge of the liver
(Fig. 1B). These findings were
confirmed on MRI performed with unenhanced and gadolinium-enhanced
sequences.
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Fig. 1B. —4-year-old boy with recurrent hepatoblastoma in orthotopic
transplanted liver. Transverse contrast-enhanced CT scan shows area of
hypoattenuation relative to normal liver parenchyma along posterior edge of
transplanted liver (arrowhead).
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PET was performed to better assess the possible presence of liver tumor.
After the patient fasted, whole-body PET was performed 50 min after the IV
administration of 147 MBq of FDG using an integrated PET–CT device
(Discovery LS, General Electric Medical Systems). PET data sets were
reconstructed iteratively with segmented correction for attenuation using the
CT data. CT images with integrated PET–CT were not evaluated for
diagnostic purposes because they were without contrast enhancement. CT images
were used only for conventional visual correlation with PET images.
Coregistered images were displayed using eNTEGRA software (General Electric
Medical Systems). The reconstructed transverse, coronal, and sagittal images
were analyzed visually; radiotracer uptake—the standardized uptake
value—was measured quantitatively by normalizing the amount of
radiotracer uptake in the lesion detected to the injected dose and patient
body weight. Standardized uptake values were calculated in the largest tumor
deposits to minimize partial volume effects.
Analysis of PET images showed an area of high radiotracer uptake along the
posterior edge of the transplanted liver that corresponded to the
hypoattenuating region depicted on contrast-enhanced CT
(Fig. 1C). Analysis also
revealed multiple areas of focal radiotracer accumulation in the liver that
had no corresponding finding on contrast-enhanced CT (Figs.
1D and
1E). Moreover, two other
nodules showing abnormally high radiotracer uptake were found in the
peritoneum; these two lesions were not identified on contrast-enhanced CT
(Fig. 1F). Additional liver
lesions and peritoneal implants were also not detectable on MRI performed
before PET. PET findings were interpreted as consistent with multiple
neoplastic lesions in the liver and peritoneum. Lung metastases, which are
common in these cases, were not seen on either FDG PET or contrast-enhanced
CT.
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Fig. 1C. —4-year-old boy with recurrent hepatoblastoma in orthotopic
transplanted liver. Transverse FDG PET–CT image shows well-defined
hypermetabolic area (arrowhead) that corresponds to hypoattenuating
region found on contrast-enhanced CT, suggesting presence of tumor tissue that
was confirmed at histopathologic analysis of gross specimen.
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Fig. 1E. —4-year-old boy with recurrent hepatoblastoma in orthotopic
transplanted liver. Transverse FDG PET–CT scan, at same level as
D, shows area of focal radiotracer accumulation in liver
(arrowhead), consistent with presence of tumor tissue that was then
confirmed at histopathologic analysis.
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Fig. 1F. —4-year-old boy with recurrent hepatoblastoma in orthotopic
transplanted liver. Transverse FDG PET–CT scan shows peritoneal nodule
characterized by abnormally high radiotracer uptake. At fine-needle aspiration
biopsy, nodule proved to be metastatic site of hepatoblastoma.
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Fine-needle aspiration biopsy of the two peritoneal nodules was carried out
under sonographic guidance. The material retrieved confirmed the presence of
viable tumor cells indicative of hepatoblastoma metastasis. Although various
chemotherapy protocols were adopted to reduce tumor progression, 5 months
after liver transplantation the patient died. After autopsy, the
histopathologic analysis of the gross specimen definitively showed the
presence of multicentric mixed hepatoblastoma in the transplanted liver, in
accordance with PET findings.
Discussion
Imaging evaluation of primary liver tumors in children has been conducted
using a wide variety of techniques, including sonography, CT, and MRI
[3–8].
Sonography is the screening technique of choice because of its sensitivity,
low cost, and general accessibility. However, sonography has relatively low
specificity in evaluating liver tumors, and it provides less anatomic detail
than CT does. On contrast-enhanced CT, the most common presentation of
hepatoblastoma includes large, diffuse, or multifocal lesions predominantly
hypodense relative to normal hepatic parenchyma, occasionally characterized by
calcifications and septations, which may help differentiate hepatoblastoma
from other liver neoplasms in children
[3]. CT with contrast
enhancement is the technique currently used to diagnose, preoperatively
evaluate, and follow up hepatoblastoma in children. However, CT findings are
sometimes inaccurate for preoperative staging of liver tumors. King et al.
[8] found that CT cannot be
used to determine ultimate resectability of hepatoblastoma in children, nor is
preoperative scanning always accurate for defining exact lobar and segmental
involvement. In another study, Finn et al.
[7] reported that the extent of
primary malignant liver tumor was underestimated on the basis of CT findings
in two of eight children in whom CT and surgical results were correlated.
Likewise, postoperative CT has proven to have some limitations in assessing
recurrent or residual liver tumor in children
[8].
Advances in instrumentation and the development of specific surface coils
provide high-quality MRI of primary liver tumors in children. Boechat et al.
[6] have assessed the efficacy
of this technique, and their results indicate that the accuracy of MRI is
comparable with that of CT in the diagnosis and staging of these tumors. Their
report also suggests that MRI is more sensitive than CT for detecting
recurrent tumor in the postoperative period. Unfortunately, fibrosis with
chronic inflammation after surgery was seen to have signal intensity
characteristics on MRI similar to those of tumor tissue. More recently, it has
been suggested that MRI is a valuable method for assessing resectability of
liver tumors in children, but it may have limited value in distinguishing
viable from necrotic tumor tissue.
PET using FDG has been shown effective in the identification of malignant
tissue in different primary and metastatic tumor types. FDG PET can reveal the
biochemical differences between normal and malignant tissues on
high-resolution tomographic images, and it has been used as a functional
method of determining tumor viability. FDG PET can be useful for assessing the
viability of residual disease after chemotherapy, and it can also be used, as
in our patient, in the evaluation of recurrent disease. We have found that
this technique may provide additional means of evaluating liver parenchyma in
a patient with recurrent hepatoblastoma and may help detect metastatic sites
not identified by other imaging techniques, thus allowing more precise tumor
staging. In our patient, CT and MRI correctly detected the presence of
recurrent tumor along the edge of the transplanted liver but did not allow
depiction of lesions inside the liver parenchyma and peritoneal metastases:
these were detected only with PET.
In agreement with previous reports, our findings confirm that PET, by
adding metabolic information to anatomic details provided by other imaging
techniques, may help in staging tumors. The ability of PET to differentiate
malignant lesions may be excellent, as shown in several studies in which PET
identified metabolically active tumor foci with no correlates at morphologic
imaging. Also, in our case, a possible explanation for higher sensitivity for
tumor tissue shown by PET may be that positive findings on PET were correlated
with metabolic rather than morphologic changes in malignant tissue.
In conclusion, our preliminary experience suggests that in children with
hepatoblastoma, FDG PET may be a useful adjunct to CT and MRI because the
integration of functional and anatomic data may represent the most effective
method of evaluating disease status.
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Introduction
Case Report
