A 34-year-old woman whose one previous pregnancy had involved cesarian section and the delivery of a healthy male infant at term was referred to our hospital at 26 weeks of gestation on account of earlier sonographic findings which had indicated possible multicystic dysplastic kidney and sacrococcygeal teratoma. Detailed sonography revealed the presence of a large, multiseptated cystic mass at the right side of the abdomen, extending to the right buttock and lower extremity, the transverse diameter of which was much larger than that of the left (Fig. 1A). The mass demonstrated variable echo patterns; color Doppler sonography revealed no internal flow at the time of examination. For further evaluation of these complex abnormalities, MR imaging was performed using a 1.5-T superconducting unit (Signa Infinity with twin-speed dual gradient; General Electric Medical Systems, Milwaukee, Wis., U.S.A.) together with a phased array coil. After performing a localized gradient-echo sequence, T2-weighted single-shot fast spin-echo MR images (TR/TE, 1624/79; bandwidth, 31.2 kHz; field of view, 22×22 cm; matrix, 224×192; slice thickness, 5 mm; intersection gap, 0 mm; number of excitations, 0.56) were obtained in the axial, coronal, and sagittal planes; the acquisition time for each was less than 1 second. The images revealed a large, multilocular, high-signal mass in the right-side of the abdomen; displacement of the ipsilateral kidney superiorly and bowel loops to the left was noted (Figs. 1B, C). Within the mass, which extended continuously to the right buttock and right lower extremity, presenting as an extensive subcutaneous cystic mass and causing asymmetric limb hypertrophy, multiple fluid-fluid levels were noted (Figs. 1C, D). Cystic lymphangioma was indicated, and after counselling, the parents opted for termination of the pregnancy because of the poor prognosis predicted on the basis of the lesion's large size and infiltrative nature.

Postmortem examination revealed a female fetus weighing 1336 g and with a fetal karyotype of 46, XX. A large, multilocular cystic mass, containing thin-walled cysts of both clear and hemorrhagic fluid, occupied the right side of the retroperitoneum (Fig. 1E), infiltrating the adipose and muscular tissues of the buttock through the retroperitoneal space and extending to the right lower extremity. Histological examination demonstrated the presence of large, endothelial-lined vascular spaces containing lymphocytic aggregates and hemorrhagic fluid, suggesting a diagnosis of lymphangioma. No other significant abnormalities of the internal organs were identified.

Lymphangiomas are benign hamartomas of the lymphatic system, consisting of multiple dilated vessels. They arise due to a developmental defect in the lymphatic pathways, which usually develop from the sixth week of gestation, leading to the proximal dilatation of afferent channels, and can be classified histologically as one of three main types: (1) simple lymphangiomas, consisting of lymphatic capillaries; (2) cavernous lymphangiomas, made up of larger lymphatic vessels with a fibrous adventitia; (3) cystic lymphangiomas or cystic hygromas, comprising multiple cysts ranging in size from a few millimeters to several centimeters. All types may coexist within the same lesion. The cyst usually contains serous or chylous fluid, and if complicated, may have bloody or purulent contents (4). Nearly 75% of lesions are located in the head and neck, or axilla, while the other 25% involve the trunk (11%), extremities (11%), mediastinum (1%), or abdomen and genitalia (3%) (6). Abdominal lymphangiomas are reported to occur most commonly in the mesentery of the small bowel, with the retroperitoneum being the second most common site.

For a fetal lymphangioma diagnosed during the prenatal period, the overall prognosis is poor, with a mortality rate ranging from 50 to 100% (7). In 50-80% of patients affected by nuchal cystic hygromas, karyotypic abnormalities and various malformation syndromes are present. Romero et al. cited a 69% incidence of abnormal karyotypes in affected fetuses, the majority being 45, X (Turner syndrome) (8), but these features might not apply to non-nuchal lymphangiomas diagnosed in utero. Because of the paucity of available data, it is uncertain whether abdominal lymphangiomas carry a significant risk for aneuploidy (7). In our case, there was no chromosomal anomaly.

At sonography and MR imaging, cystic lymphangiomas appear as sharply defined, unilocular or multilocular cystic masses, with thin- or thick-walled septa. At sonography, the fluid may be anechoic, with enhanced through-transmission, or there may be variable internal echoes or fluid-fluid levels, due to bleeding and fibrin deposition (9). In our case, fetal sonography and MR imaging accurately identified the lymphangioma and defined its anatomical location and extent, thus providing the information essential for parental counselling. Because of its accuracy and safety, as well as its low cost and real-time capability, and the fact that it is easy to use, sonography has been regarded as the imaging modality of choice for the prenatal assessment of fetal abnormalities. Its inherent disadvantages include, however, operator-dependency and a limited field of view (10). With recent technical advances in ultrafast MR imaging, the modality has become a useful tool for prenatal diagnosis, particularly for the assessment of complex fetal abnormalities. In this case, single-shot fast spin-echo MR imaging clearly demonstrated fetal abnormality and helped make the correct prenatal diagnosis. In addition, MRI allowed more comprehensive imaging of the fetus because of its larger field of view, and accurately delineated the extent of the mass.

To our knowledge, published reports have described three cases in which a fetal abdominal lymphangioma extending to an extremity was diagnosed by prenatal sonography, as in our case (2). This extension reflects the pathway of the normal developing lymphatic system and may be typical of retroperitoneal lymphangiomas. In all three cases, pregnancy was terminated, in view of the poor prognosis. In contrast, postnatal surgical resection or sclerotherapy was successfully performed in four reported cases of fetal abdominal lymphangiomas confined to the abdominal cavity or abdominal wall (2).

For the postnatal treatment of abdominal lymphangioma, the preferred treatment is surgical extirpation, with careful preservation of involved structures. Large but localized lymphangiomas can be excised completely, but the surgical treatment of diffuse and multiple lesions is extremely difficult and is associated with high morbidity and mortality (6). For the treatment of surgically unresectable lesions, the injection of a sclerosing agent is considered appropriate: successful outcomes have been reported following the use of intralesional bleomycin, sclerotherapy with OK-432, or percutaneous embolization with Ethibloc (2, 11). The successful intrauterine treatment of a cystic hygroma with OK-432 has also been reported (12).

In conclusion, prenatal MR imaging was valuable in the detection, characterization, and exact evaluation of the extent of an extensive fetal lymphangioma, and complemented the role of sonography.