Mediastinal tumors are a heterogeneous group of benign and malignant neoplasms that have in common their localization in the mediastinum. Primary mediastinal tumors in children are rare.^[1,2] Depending on their localization in the mediastinum (anterior, middle, or posterior), an assumption can be made on their origin and etiology.^[2,3] Extragonadal germ cell tumors are more common in neonates and infants compared to adolescents, where the gonads are usually affected.^[4] Congenital mediastinal teratomas are very rare, and their presentation may be diverse based on their size, location, malignancy, and growth rate.^[4,5]

The aim of this case report was to present a rare case of primary mediastinal tumor in a newborn leading to acute respiratory distress and hemodynamic instability in the immediate postnatal period.

We present a newborn female from a second pregnancy who was delivered vaginally at 35 weeks gestation, weighing 3100 grams at birth, and measuring 50 cm in length. There was no documentation of antenatal care. The Apgar score was low (5 at 1 minute, 6 at 6 minutes) because of cyanosis and respiratory distress symptoms. Mechanical ventilation was initiated in the delivery room after the child was intubated. The physical examination revealed hepatomegaly, symmetrical peripheral pulses on the limbs, a grade 3/6 ejection systolic murmur audible over the precordium, reduced lung sounds on both sides, and bronchial obstruction. Large, uniform, dense shadows were seen in the right middle and left superior lung fields on the chest x-ray(Fig. 1). There were no significant changes in the ECG with sinus rhythm, normal for age right-axis deviation, or low-voltage QRS complexes. The echocardiography revealed a large cystic mediastinal tumor mass that compressed the right atrium and right ventricular outflow tract (RVOT), resulting in RVOT obstruction with a Doppler measured peak gradient of 60 mmHg. The right ventricle was hypertrophied (right ventricular free wall – 6 mm, z-score +6), with impaired diastolic function and an E/A index of 0.6. The patient had moderate tricuspid regurgitation and an elevated right ventricular systolic pressure of 60 mmHg. An MRI was performed, which confirmed the presence of a large multicystic formation in the anterior mediastinum from the upper thoracic aperture to the right diaphragm, measuring 85×51 mm axially and 83×49 mm coronally(Fig. 2). No calcifications or adipose collections were visualized. Capsule presence was suspected based on the finding of peripherally distributed venous contrast with nonhomogeneous contrasting of the internal septae. The tumor mass compression on the respiratory tract and lung parenchyma was noted, with the superior bronchi not visualized. The superior vena cava, right ventricle (RV), and the supra-aortic arterial and venous vessels were compressed. The provisional diagnosis was a tumor mass originating from the thymus. Congenital cystic pulmonary airway malformation (CPAM) and lymphatic malformation were considered in the differential diagnosis.

The case was discussed with a multidisciplinary team including a radiologist, pediatrician, neonatologist, pediatric cardiologist, anesthesiologist, thoracic surgeon, and cardiac surgeon. A decision for surgical extirpation of the formation on an urgent basis was made. Due to the specific location of the tumor in the mediastinum and the proximity to the heart and great vessels, the operation was scheduled in the National Heart Hospital, where cardiopulmonary bypass standby was provided. During the operation, the mass was resected in two sections intimately connected at the midline, each measuring 5×5 cm and 3×3 cm(Figs 3, 4) .

Histopathology showed mature cystic teratoma, composed of endo- and mesodermal tissue. There was a lack of ectoderm and immature neoplastic tissue.

Postoperatively, the patient was in a stable condition. The ultrasound examination demonstrated a normal blood flow pattern with no obstruction in the right ventricular outflow tract (peak velocity 1.2 m/sec) and normalized right ventricular systolic pressure. The early postoperative period was complicated by systemic infection and respiratory distress with left lung atelectasis due to left phrenic nerve palsy, requiring intubation and prolonged mechanical ventilation. After extubation, the patient was placed on non-invasive ventilation and discharged at 58 days post-surgery. At routine ambulatory examination, the child’s physical and neurologic development was normal. The ultrasound examination showed normal heart function and no evidence of tumor relapse.

The study was approved by the Committee of Medical and Academic Ethics, which confirmed that no identifiable patient information was mentioned in the publication and that the publication of this case report followed the regulations of the European Charter for Researchers. Written informed consent was obtained from the patient’s legal guardian for publication.

Primay mediastinal tumors in children are extremely rare. A study including 110,284 adult and pediatric patients with primary neoplasms demonstrated that 22 (0.02%) cases were pediatric mediastinal tumors.^[1] Symptomatic mediastinal tumors in the neonatal period are even rarer. Often the diagnosis can be established prenatally at the routine ultrasound examination. The origin of the tumor mass may be suspected based on its localization in the mediastinum. In the anterior mediastinum, the frequency is the highest for lymphomas, germ cell tumors, and thymomas; in the middle mediastinum, it is lymph nodes, lymphomas, and cysts; and in the posterior mediastinum, the most common tumor masses are neurogenic tumors and those with origin from the primary gut.^[2,3]

Germ cell tumors are the third most common mediastinal tumors in children after lymphomas and neurogenic tumors.^[2] They encompass 6%–18% of tumor masses in the anterior mediastinum.^[2] Teratomas are the most common germ cell tumor in the mediastinum, accounting for up to 60% of cases.^[3] Depending on their level of differentiation, they are divided into four categories from grade 0, fully differentiated teratomas containing only mature tissue, to grade 3, with the presence of more than 50% immature neuroepithelium.^[3] The more immature a teratoma, the higher the risk of malignant presentation and relapse.^[2] On chest x-rays, teratomas present as rounded, well-defined structures in the anterior mediastinum with the presence of calcification in 25%–53% of cases.^[4] The hallmarks of teratomas on computer tomography (CT) or magnetic resonance imaging (MRI) are the presence of liquid, fat, and calcification regardless of their grade.^[2] It is typical for malignant tumors to invade neighboring structures, whereas mature teratomas are usually sharply marginated with a tendency to displace rather than invade adjacent structures.^[4]

Germ cell tumors are the fifth most common malignant neoplasms in the neonatal period following neuroblastoma, leukemia, nephroblastoma, and retinoblastoma.^[2] In contrast to children and adolescents, where the gonads are the most common localization, neonates have predominantly extragonadal masses.^[2] In a retrospective research of 534 neonates and fetuses, Isaacs^[5] showed that the mediastinal localization of teratomas is rare – 2.6%. The most common site in this age group is the sacrococcygeal teratoma (40%).^[5] For the clinical presentation, the size and the growth rate of the mass are more important than the type of the tumor. The presence of a mediastinal mass can be identified prenatally at the routine fetal ultrasound. Prenatally, there may be a lack of symptoms, but it may also present as non-immune hydrops fetalis or intrauterine death, commonly due to compression of vital organs and the cardiovascular system.^[3,6,7] After delivery, the mediastinal tumor might cause acute respiratory distress syndrome, superior vena cava syndrome, cardiac tamponade, and pleural or pericardial effusion.^[2,8,9] Different imaging techniques (ultrasound, CT, MRI) are necessary to establish the diagnosis and may be used as diagnostic clues pointing to the origin of the mass based on its localization.^[4] Serum tumor markers alpha-fetoprotein (AFP) and β-hCG are commonly elevated in germ-cell tumors and can be used as a supplementary diagnostic tool and for risk stratification.^[4,8]

The gold standard for primary mediastinal tumor treatment in neonates, irrespective of their localization, is surgical excision. The presence of microscopic residual tissue does not lead to a higher incidence of relapse or death.^[5] Chemotherapy and radiotherapy are indicated in complicated cases with advanced disease, complementary to surgery.^[5,6] Due to the close proximity of the phrenic nerve to the great vessels, there is a risk of injury during surgical excision of the tumor. Stajevic et al. reported a similar case of a neonate who postoperatively required plication of the left diaphragm due to paradoxical movement.^[10] Overall postoperative complications are rare. In a retrospective analysis of 108 adult patients with benign mediastinal teratomas, there were no surgical deaths. They reported single cases of massive bleeding, chylothorax, recurrent laryngeal nerve injury, wound infection, and pulmonary infection.‌^[11] There is no standard follow-up schedule, but for patients with sacrococcygeal teratoma, serial measurement of serum tumor markers for at least 3 years postoperatively is recommended in addition to routine clinical and imaging exams (ultrasound and MRI depending on the localization) to facilitate early detection of tumor relapse.^[12]