A 31 year-old G1,P0 patient was referred to the fetal medicine clinic at 28 weeks of gestational age due to a fetal intraabdominal tumor identified in an ultrasound examination done previously. A detailed examination of the fetal anatomy did not reveal any further anomalies.

These are two video clips:

The following are images obtained during ultrasound scan:

The first video clip demonstrates a transverse view of a well-defined echogenic mass. The second video demonstrates a longitudinal view of the echogenic mass, seen below the diaphragm.

The following are the additional images that were obtained by pre-natal MRI to confirm the mass over the left supra-renal gland.

Fetal MRI with T2-weighted sequences in the sagittal, axial and coronal planes. Note the expansive, heterogeneous, macrolobulated, predominantly hyperechoic lesion containing cysts in its lower portion. The lesion is in the lower third of the left hemithorax and crosses the mid-line, pushing the heart forward and the aorta posteriorly; it also dislocates the diaphragm, the stomach and the spleen caudally.

The first hypothesis was neuroblastoma, with lung sequestration as a differential diagnosis. As fetal conditions were stable, surgical delivery was planned at 38 weeks of gestation. At 25 days the neonate underwent a second MRI, which showed similar findings to those found on pre-natal imaging.
T1 and T2-weighted coronal images, showing that the lesion is hypodense in the imaging sequence with a short TR and hyper dense in the imaging sequence with a long TR. The lesion is lobular, containing cysts and trabeculae and pushes down the spleen and the left kidney.

Sagittal T2 and post-contrasts gradient echo T1 images, showing the T2 hyperintense lesion with discrete areas of anomalous enhancement following endovenous paramagnetic contrast (Gd-DTPA). The lesion is in the thoracic and abdominal compartments.

T2-weighted axial images with and without fat suppression, showing that the lesion remains hyperintense, excluding a possible lipid nature. The lesion pushes the aorta to the right; there are no signs of vascular infiltration.

A gradient echo post-contrast T1 coronal image, demonstrating discrete areas of anomalous enhancement. The lesion crosses the mid-line to the right.

Surgical resection of the tumor was undertaken at 30 days of age through a retroperitoneal approach. This photograph shows the mass and adrenal during laparotomy.

Dissection of the cranial pole of the tumor subdiaphragmatically, advancing towards the mediastinum:

The macroscopic aspect suggested lung sequestration measuring 7.8 x 4.1 cm, confirmed later by histopathology.

Histology demonstrates dilated alveolus with ciliated columnar epithelium:

At 3 months now, the child is healthy, confirming the favorable prognosis of extralobar lung sequestration with no fetal hydrops or associated malformations.

In this case, as in most that have been published to date, the final diagnosis was only established by the histopathological examination of the resected tumor. Furthermore, there was increased diagnostic difficulty during gestation due to the less frequent subdiaphragmatic and retroperitoneal location of lung sequestration.