Ultrasound Diagnosis of a Subcutaneous Cystic Formation in the Fetal Thorax

SECTION 2 – ANSWER Case description A 39-year-old pregnant woman, primigravida, was referred to our obstetric department in the first trimester of pregnancy for pregnancy surveillance due to her age. First-trimester combined screening reported a low risk for trisomies 13 and 18 and an intermediate risk for trisomy 21 of 1 in 398. After prenatal counseling, the parents refused amniocentesis and opted for cell-free fetal DNA testing, which showed a low risk for fetal 13.18 and 21 aneuploidies. The 21-week scan showed a live female fetus showing a subcutaneous left thorax edema up to the abdominal region measuring 60 mm × 20 mm × 15 mm without blood flow on color Doppler [Figures 1 and 2]. No other fetal anatomical abnormalities were seen during the scan. The placenta was located on the posterior wall of the uterus, and the amniotic fluid was normal.Figure 1: Twenty one week ultrasound: Sagittal plane of fetal thorax showing a multilocular tumefactionFigure 2: Twenty one week ultrasound: Transverse plane of fetal thorax showing a multilocular tumefactionDue to the findings, prenatal counseling was provided, and amniocentesis was performed at 22 weeks. Quantitative fluorescent polymerase chain reaction (QF-PCR), array- comparative genomic hybridisation (CGH), and TORCH group testing were ordered, and a fetal echocardiogram was also performed. A complementary magnetic resonance study was requested at 29 weeks of gestation that showed a cystic formation in the left thorax wall, multiseptate, with no blood flow on color Doppler, measuring 58 mm × 46 mm × 20 mm, without mass effect on the underlying structures [Figure 3].Figure 3: Magnetic resonance imaging at 29 weeks: Coronal and transverse planes of the fetus. The tumefaction is indicated by the arrowThe 34-week scan showed normal fetal growth and amniotic fluid volume and the cystic mass with 60 mm × 50 mm × 30 mm without apparent muscular or bone invasion [Figure 4]. Following prenatal counseling, a cesarean delivery was determined as the mode of delivery.Figure 4: Thirty four week ultrasound: Sagittal plane of the fetal thorax tumefaction in the third trimesterThe pregnant woman underwent urgent cesarean delivery at 36 weeks and 4 days after preterm premature rupture of membranes, and a 2765 g female infant was delivered with an APGAR score of 9/10/10 [Figure 5]. The patient postoperative course was uncomplicated, and both were discharged at day 3 after delivery.Figure 5: Newborn with a left thoracic wall tumefaction indicated by the arrowINTERPRETATION Second-trimester ultrasound revealed a 6-cm subcutaneous cystic formation on the left side of the fetal thorax, with anechoic content and no signs of vascularization on color Doppler. No other morphological or functional abnormalities were observed. Differential diagnoses included fetal lymphangioma, congenital pulmonary airway malformation, teratoma, congenital heart disease, and chylothorax. Amniocentesis was performed, and QF-PCR, array-CGH, and TORCH screening showed normal results. The fetal echocardiogram was also normal. At 29 weeks, magnetic resonance imaging (MRI) confirmed a laterally exophytic cystic formation (58 mm × 46 mm × 20 mm), multiloculated, with no mass effect on adjacent structures, highly suggestive of fetal lymphangioma. At 34 weeks, the mass remained stable in size, with no other changes on the ultrasound. With the diagnosis of fetal chest lymphangioma, a cesarean delivery was planned to avoid potential injury to the cystic structure during vaginal delivery. DISCUSSION Fetal lymphangiomas, with a reported prevalence of 1.1–5.3 cases per 10,000 births, are benign tumors of lymphatic vessels that involve the skin and subcutaneous tissue and might have the potential to infiltrate surrounding structures.[1,2] They typically develop between the end of the first trimester and the early second trimester and are discovered during obstetric ultrasound in up to 65% of cases.[3,4] The vast majority of these lesions occur in the neck (75%–80%), typically referred to as cystic hygroma, a condition that may be associated with aneuploidies, particularly Turner syndrome and trisomies 21, 18, 13, as well as triploidy.[1,5] Lymphangiomas may also occur in the axillary region (20%) and in rarer locations such as the thorax, abdominal wall, and limbs.[2,5,6] As a significant association between lymphangiomas and chromosomal abnormalities has been reported in the literature, it is recommended that a karyotype examination, along with serial detailed ultrasound scans, be performed upon diagnosis.[2] These should monitor lesion growth, fetal anatomical malformations, signs of compression of adjacent structures, and amniotic fluid volume. MRI may also be useful in assessing the extent of lymphangioma invasion.[1,4] Fetal thorax lymphangioma is a rare malformation with only few cases reported in the literature, and this malformation is usually not associated with abnormal karyotype or other anatomical malformations.[2,6] Prognosis is generally favorable unless there is associated cardiac failure, hydrops, or signs of high airway compression.[2,6,7] Preferred treatment for fetal chest lymphangiomas is complete surgical removal. Recurrence might be common if the lesion has infiltrated the subcutaneous layer.[2,4] Small lymphangiomas may be managed with a watchful approach – if there is no esthetic affectation, functional deficiency, or associated symptoms. Recent developments in sclerotherapy have expanded the range of available treatment options, including its use as an option.[2,4,5] In conclusion, obstetric ultrasound is crucial for the diagnosis and monitoring of fetal lymphangiomas. Although fetal thorax lymphangioma is a rare malformation, the presence of this condition warrants a detailed and serial obstetric ultrasound to rule out other anomalies, as well as a fetal genetic study. Prognosis is generally favorable in the absence of other abnormalities, and surgical removal is the favored treatment. Ethics statement This study was conducted in accordance with the ethical principles outlined in the Declaration of Helsinki and its amendments. The authors certify that they have obtained all appropriate patient consent forms. In the form, the patient has given her consent for her images and other clinical information to be reported in the journal. The patient understands that her name and initials will not be published and due efforts will be made to conceal her identity, but anonymity cannot be guaranteed. Financial support and sponsorship Nil. Conflicts of interest There are no conflicts of interest.