Imaging of fetal tumors and other dysplastic lesions: A review with emphasis on MR imaging

Diagnostic magnetic resonance imaging characteristics of congenital mesoblastic nephroma: a retrospective multi-center International Society of Pediatric Oncology-Renal Tumor Study Group (SIOP-RTSG) radiology panel study

BACKGROUND

Congenital mesoblastic nephroma is the most common solid renal tumor in neonates. Therefore, patients <3 months of age are advised to undergo upfront nephrectomy, whereas invasive procedures at diagnosis in patients ≥3 months of age are discouraged by the International Society of Pediatric Oncology-Renal Tumor Study Group (SIOP-RTSG). Nevertheless, discriminating congenital mesoblastic nephroma, especially from the more common Wilms tumor, solely based on imaging remains difficult. Recently, magnetic resonance imaging (MRI) has become the preferred modality. Studies focusing on MRI characteristics of congenital mesoblastic nephroma are limited.

OBJECTIVE

This study aims to identify diagnostic MRI characteristics of congenital mesoblastic nephroma in the largest series of patients to date.

MATERIALS AND METHODS

In this retrospective multicenter study, five SIOP-RTSG national review radiologists identified 52 diagnostic MRIs of histologically proven congenital mesoblastic nephromas. MRI was performed following SIOP-RTSG protocols, while radiologists assessed their national cases using a validated case report form.

RESULTS

Patients (24/52 classic, 11/52 cellular, and 15/52 mixed type congenital mesoblastic nephroma, 2/52 unknown) had a median age of 1 month (range 1 day-3 months). Classic type congenital mesoblastic nephroma appeared homogeneous with a lack of hemorrhage, necrosis and/or cysts, showing a concentric ring sign in 14 (58.3%) patients. Cellular and mixed type congenital mesoblastic nephroma appeared more heterogeneous and were larger (311.6 and 174.2 cm3, respectively, versus 41.0 cm3 for the classic type (P<0.001)). All cases were predominantly T2-weighted isointense and T1-weighted hypointense, and mean overall apparent diffusion coefficient values ranged from 1.05-1.10×10-3 mm2/s.

CONCLUSION

This retrospective international collaborative study showed classic type congenital mesoblastic nephroma predominantly presented as a homogeneous T2-weighted isointense mass with a typical concentric ring sign, whereas the cellular type appeared more heterogeneous. Future studies may use identified MRI characteristic of congenital mesoblastic nephroma for validation and for exploring the discriminative non-invasive value of MRI, especially from Wilms tumor.

Prenatal MRI diagnosis and outcomes of abdominal or sacrococcygeal teratomas and parasitic fetuses

Objective

To investigate the MRI findings of fetal abdominal or sacrococcygeal teratomas and parasitic fetuses and analyze the outcomes on the basis of follow-up assessments.

Methods

The MRI data of 60 cases of abdominal or sacrococcygeal masses were examined. The outcomes were followed up and compared with the prenatal MRI diagnoses.

Results

The 60 cases included 52 cases of sacrococcygeal teratomas and eight cases of abdominal lesions. The common types of sacrococcygeal teratomas were type I (21/52, 40.4%) and type II (20/52, 38.5%); type III sacrococcygeal teratomas were rarer (8/52, 15.4%), while type IV tumors (3/52, 5.7%) were frequently complicated with hydronephrosis. Other complications included polyhydramnios in 22 cases, placental edema in six cases, and fetal hydronephrosis in three cases (all type IV). Seven of the eight parasitic fetuses were located in the abdominal cavity, and one was located in the sacrococcygeal region. Postnatal surgery was performed in 51 cases (51/60), including 44 with teratomas and seven with parasitic fetuses. In one case with hydronephrosis, peritoneal effusion, and subcutaneous edema, treatment was discontinued after birth (1/60). Fetal induction of labor was observed in eight cases (8/60). Prenatal ultrasound yielded incorrect or ambiguous diagnoses in 11 cases, while 51 cases showed a favorable course after surgery.

Conclusions

MRI shows high accuracy in the diagnosis of fetal sacrococcygeal teratomas and parasitic fetuses. The prognosis in these cases is generally good. However, type IV sacrococcygeal teratomas are prone to fetal hydronephrosis and misdiagnosis and show a poorer prognosis.

Magnetic resonance imaging of fetal abdominal pathology: a complementary tool to prenatal ultrasound

Fetal magnetic resonance imaging (MRI) is increasingly being used worldwide as a complementary tool to prenatal ultrasound (US) for multiple fetal pathologies. The aim of this article is to describe and illustrate how MRI can help US to evaluate fetal abdominal anomalies, based on cases performed in a tertiary public university hospital. Prenatal US, fetal MRI and postnatal imaging of these cases will be shown side-by-side to describe and illustrate the added value of fetal MRI in the different organs/systems and its impact on clinical management.

An Unusual Antenatal Presentation of a Mature Pericardial Teratoma Masquerading as Congenital Pulmonary Airway Malformation

We report an antenatal presentation of a huge pericardial mature teratoma that was referred as congenital pulmonary airway malformation (CPAM) in the late third trimester of pregnancy. Initial ultrasound evaluation revealed a huge predominantly cystic lesion with mixed echogenicity in the left hemithorax. A provisional diagnosis of pleural tumor was considered in view of previous scans at 20‒28 weeks being normal and associated pleural effusion. Magnetic resonance imaging of the fetus reported the lesion to be CPAM which was supported by postnatal computed tomographic imaging done on day 2 of life. However, intraoperatively, the lesion was found to be of pericardial origin which on subsequent histopathological examination was confirmed to be mature teratoma. We recommend considering potential differential diagnosis other than CPAM, especially when the lesion is found for the first time in the late third trimester.

Fetal imaging of congenital lung lesions with postnatal correlation

Congenital lung lesions are a rare group of developmental pulmonary abnormalities that are often first identified prenatally on routine second-trimester US. Congenital pulmonary airway malformation (CPAM) is the most common anomaly while others include bronchopulmonary sequestration, congenital lobar overinflation, bronchogenic cyst and bronchial atresia. Clinical presentation is highly variable, ranging from apparent in utero resolution to severe mass effect with resultant hydrops fetalis and fetal demise. Differentiation among these lesions can be challenging because overlapping imaging features are often present. The roles of the radiologist are to identify key imaging findings that help in diagnosing congenital lung lesions and to recognize any ominous features that might require prenatal or perinatal intervention. High-resolution US and complementary rapid-acquisition fetal MRI provide valuable information necessary for lesion characterization. Postnatal US and CT angiography are helpful for lesion evaluation and for possible surgical planning. This article reviews the embryology of the lungs, the normal prenatal imaging appearance of the thorax and its contents, and the prenatal and neonatal imaging characteristics, prognosis and management of various congenital lung lesions.

The Clinical Value of Prenatal Ultrasonography in the Differential Diagnosis of Fetal Suprarenal Space-Occupying Lesions

Objective

This study aimed to investigate the value of prenatal ultrasonography in the differential diagnosis of fetal space-occupying lesions in the adrenal gland.

Methods

Thirty-six fetuses with adrenal gland space-occupying lesions diagnosed by prenatal ultrasonography between January 2019 and July 2021 were included in this retrospective study. The clinical data, ultrasonographic features, treatments, and prognoses of the fetuses were analyzed. Postnatal diagnoses were made using computed tomography (CT), magnetic resonance imaging, and surgical resection.

Results

Of the 36 fetuses, 10 were diagnosed with adrenal hematomas, eight with adrenal neuroblastomas, seven with adrenal cysts, seven with subphrenic pulmonary sequestration, and four with adrenal teratomas. The accuracy of prenatal diagnosis was highest in those with adrenal cysts and subphrenic pulmonary sequestration, with the accuracy being 85.7% for both conditions. The mean gestational age at first detection of subphrenic pulmonary sequestration was 22.5 ± 3.1 weeks, which was significantly lower than that of other diagnoses (P < 0.05), and the mean diameter of adrenal cysts was 15.1 ± 4.2 mm, which was significantly smaller than that of other lesions (P < 0.05). All newborns with adrenal teratomas and neuroblastomas were treated surgically. Five of the seven patients with subphrenic pulmonary sequestration and three of the seven patients with cysts were also treated surgically. Follow-ups of the remaining cases were carried out by enhanced CT examination, and the prognoses were good.

Conclusion

Prenatal ultrasonography can help differentiate between different types of fetal adrenal space-occupying lesions, and there is a high coincidence rate between the diagnosis of adrenal cysts and subphrenic pulmonary sequestration.

Combination of volume-rendering 3D surface modeling and medical illustration to capture the living fetus

OBJECTIVE

A good medical illustration renders essential aspects of a procedure or condition faithfully, yet idealizes it enough to make it widely applicable. Unfortunately, the live fetus is generally hidden from sight, and illustrating it relies either on autopsy material or manipulated newborn images. High-definition volume rendering of diagnostic imaging data can represent hidden conditions with an almost lifelike realism but is limited by the resolution and artifacts of the data capture. We have combined both approaches to enhance the accuracy and didactic value of illustrations of fetal conditions.

METHODS

Three examples, of increasing complexity, are presented to demonstrate the creation of medical illustrations of the fetus based on semiautomatic computerized posthoc manipulation of diagnostic images.

RESULTS

The end product utilizes the diagnostic accuracy of ultrasound and magnetic resonance imaging of the fetuses and the spatial manipulation of 3D models to create a lifelike, accurate and informative image of the fetal anomalies.

CONCLUSION

Volume-rendering and 3D surface modeling can be combined with medical illustration to create realistic and informative images of the developing fetus, using a level of detail that is tailored to the intended audience.