Keywords
antenatal - fetal - ganglioneuroblastoma - neuroblastoma - tumor
Introduction
Neuroblastoma, ganglioneuroblastoma, and ganglioneuroma form a spectrum of neuroblastic
tumors originating from the neural crest derived progenitor cells or neuroblasts,
the precursor for ganglion cells in the sympathetic nervous system.[1]
[2] These tumors exhibit diverse outcomes, ranging from spontaneous regression to fatal
disease.[3]
[4]
Neuroblastomas, though common in the neonatal period, are rarely diagnosed prenatally.
Sixty to 90% of fetal neuroblastomas are situated in the adrenal glands; hence, the
presence of a fetal suprarenal solid or cystic mass is a strong indicator of neuroblastoma.[5]
Case Report
A 30 year old primigravida with no history of significant medical issues or hypertension
underwent a routine growth scan at 33 weeks of pregnancy. Her first trimester nuchal
translucency scan and the anomaly scan at 20 weeks showed normal results.
Ultrasound examination showed a well margined hypoechoic lesion in the midline retroperitoneum,
displacing the inferior vena cava to the right. On grayscale imaging, the lesion appeared
solid, without any apparent cystic component or large calcifications, although few
faint internal calcifications were detected within the mass ([Fig. 1A, B]). Doppler imaging did not reveal significant internal vascularization or feeder
vessels from the descending aorta ([Fig. 1C]). A preliminary diagnosis of a fetal abdominal tumor was made, with neuroblastoma
and extralobar pulmonary sequestration in the list of potential differential diagnoses.
Fig. 1 (A, B) Ultrasound of fetal abdomen in axial and coronal planes, identifying a hypoechoic
mass in the midline in retroperitoneum (N) at 33 weeks of gestation. (C) Color Doppler image shows no obvious blood flow within the lesion or any feeder
vessel from the aorta.
Further assessment with fetal magnetic resonance imaging (MRI) confirmed a well defined
T2 intermediate signal intensity lesion in the midline retroperitoneum at the level
of the kidneys ([Fig. 2A, B]). It displaced the aorta posteriorly and the inferior vena cava to the right. No
intraspinal extension was observed. The calcific foci in the lesion and the absence
of systemic feeder vessels favored fetal neuroblastic tumor over extralobar pulmonary
sequestration.
Fig. 2 (A, B) Fetal magnetic resonance imaging (MRI) T2-weighted (axial and coronal views), showing
an intermediate signal intensity lesion (arrowheads) in the retroperitoneum at the
level of the fetal kidneys.
A cesarean section was performed at 38 weeks for an obstetric indication, delivering
a male child. The neonate exhibited no abdominal distension, organomegaly, additional
swellings, or feeding difficulties. At 1 month, an ultrasound revealed a heteroechoic
mass in the right paramedian retroperitoneum, larger compared to the antenatally detected
lesion ([Fig. 3A]). A trucut biopsy from the mass showed two morphological components; neuroblasts
with monomorphic round cells with uniform nuclei and salt pepper chromatin, as well
as ganglion cells with abundant granular eosinophilic cytoplasm and distinct cell
boundaries. On immunohistochemistry, the neuroblasts were positive for synaptophysin
and chromogranin while the ganglion cells were positive for S100 and glial fibrillary
acidic protein. This confirmed the diagnosis of ganglioneuroblastoma. Considering
the potential for spontaneous regression of antenatally detected neuroblastic tumors,
a conservative approach without surgery or chemotherapy was opted for.
Fig. 3 (A) Postnatal ultrasound at 1 month, showing a larger heteroechoic mass in the right
paramedian retroperitoneum. (B) Follow up postnatal ultrasound at 5 months, showing a decrease in the size of mass.
At 5 months, follow up ultrasound showed a decrease in the mass size accompanied by
normalized urinary vanillylmandelic acid and homovanillic acid levels ([Fig. 3B]). By 8 months, the retroperitoneal mass was barely discernible on ultrasound, and
the infant remained asymptomatic and active during the follow up period.
Diagnostic Parameters
Fetal tumors are rare and present challenges due to various possible diagnoses and
unpredictable course during pregnancy and infancy. Prognosis depends on factors like
tumor type, location, and size, with most having poor outcomes. However, some exceptions
like fetal neuroblastic tumors have a better prognosis.[3] Neuroblastoma, the most common childhood extracranial solid tumor, can also be detected
incidentally in late pregnancy. Typically, they present as a well defined solid suprarenal
mass on ultrasound, though some may be cystic. Microcalcifications and intratumoral
hemorrhage are also seen.[6]
MRI can be a complementary tool to help confirm the anatomic location and to exclude
adrenal hemorrhage. It is also useful for staging and evaluating metastases, which
most frequently involve the liver and the placenta.[7]
Differential diagnoses include subdiaphragmatic extralobar pulmonary sequestration,
teratoma, adrenal hemorrhage, and renal and pancreatic tumors.[1]
[5]
[8]
Subdiaphragmatic extralobar pulmonary sequestration is more common than neuroblastoma,
typically appearing echogenic, left sided, and identifiable in the second trimester.
In contrast, neuroblastic tumors can be either solid or cystic, often appearing on
the right side, and are typically identified in the third trimester. Neuroblastic
tumors may show calcifications, unlike pulmonary sequestration. Doppler flow studies
may help distinguish between them as neuroblastic tumors lack a single feeding vessel.[9]
Adrenal hemorrhage shows variable appearance, ranging from an echogenic lesion to
a cystic suprarenal mass, typically changing appearance on follow up.[9] Teratoma has a more heterogeneous appearance with irregular cystic areas, large
irregular calcifications, and, occasionally, identifiable bony structures.[9]
The overall prognosis of neuroblastoma detected during the fetal stage is excellent,
with a 90 to 100% survival rate.[10] Spontaneous regression and maturation to more differentiated forms of neuroblastic
tumors have been described and take on average 6 to 12 months. The mechanism of regression
is unknown.[10]
Conclusion
We present a case of a retroperitoneal neuroblastic tumor, tracing its progression
from prenatal diagnosis during the third trimester of pregnancy until its regression
at eight months of age. This case study highlights the favorable prognosis for neuroblastic
tumors identified during pregnancy due to their potential for resolution without surgical
interventions or chemotherapy. Furthermore, it underscores the diagnostic and prognostic
importance of ultrasound and MRI imaging in fetal tumors.
