Introduction
Yolk sac tumours (YSTs), also known as endodermal sinus tumours, are a class of malignant germ cell tumours and are the most common histologic type of extragonadal germ cell tumours (EGGCTs) in children[
1,
2,
3]. While primary sites in the testis and ovary are more common, primary mediastinal YSTs (or EGGCTs) are extremely rare in the paediatric population[
1]. These tumours often present acutely with mass effect on the intrathoracic structures (i.e., trachea, bronchi, superior vena cava, pericardium), and, because of their aggressive behaviours and nonspecific respiratory symptoms, require urgent diagnosis and treatment to prevent morbidity and mortality[
4].
This report outlines a case of anterior mediastinal YST in a toddler with acute respiratory distress. The clinical course, diagnostic investigations, treatment plan, and family psychosocial issues will be presented in the context of existing literature and best practices.
Case presentation
A previously healthy 2-year-and-5-month-old boy presented to the emergency department (ED) with a 1-week history of dry cough, decreased oral intake, and progressive respiratory distress. At the time of presentation, he was tachypnoeic, lethargic, and using accessory muscles, with an oxygen saturation of 94% on high-flow nasal cannula (HFNC).
A chest X-ray was performed, which demonstrated a widened mediastinum and opacification on the right side. CT scan revealed a 6.7 cm × 5.2 cm anterior mediastinal mass compressing the trachea and right main bronchus, with associated right lung collapse. The risk of airway obstruction from the mass was high, and intubation was performed in a controlled setting in the paediatric intensive care unit (PICU), with anaesthesia and intensive care support (Table 1).
The boy was initiated on broad-spectrum antibiotics (meropenem, vancomycin, caspofungin) for suspected nosocomial pneumonia. CT-guided core biopsy of the mass revealed a yolk sac tumour (Figure 1), confirmed by histology and positive immunohistochemistry for alpha-fetoprotein (AFP). The serum AFP was also markedly elevated at 9200 ng/mL (Table 2). No extrathoracic metastases were identified on staging imaging (brain and abdominal ultrasonography.
He initiated BEP chemotherapy (bleomycin, etoposide, cisplatin) on hospital day 5. By day 10, his AFP fell to 4300 ng/mL. He tolerated chemotherapy well and did not have significant renal or pulmonary toxicity. Laboratory monitoring during and after chemotherapy revealed stable renal function (serum creatinine: 0.4–0.5 mg/dL; blood urea nitrogen: 12–15 mg/dL) and no electrolyte disturbances. Urine output remained within normal limits throughout hospitalization. Pulmonary status was closely observed due to bleomycin use. The patient-maintained oxygen saturation between 97%–99% on room air after extubation, and follow-up chest radiography at discharge showed no new interstitial changes or infiltrates suggestive of pulmonary toxicity (Figure 2).
Owing to the patient’s young age, formal pulmonary function testing was not feasible; however, serial clinical assessments and imaging demonstrated no evidence of bleomycin-related pulmonary injury.
He was extubated on day 18 and progressively transitioned to oral feeding. During hospital care, he was given supportive care including psychosocial interventions, and he was discharged on day 24 with an outpatient oncology referral for continued treatment.
After completion of the initial BEP chemotherapy cycle, the patient showed full remission of respiratory symptoms and no longer required supplemental oxygen. A follow-up chest X-ray at discharge demonstrated a marked reduction in the mediastinal widening and re-expansion of the right lung, consistent with a strong partial radiologic response. These findings correlated with the significant decline in serum AFP levels. The chest X-ray taken at discharge has now been included as (Figure 2) to objectively illustrate the treatment response.
Discussion
YSTs are highly aggressive malignant germ cell tumours, primarily affecting young males[
2,
3]. Their central thoracic location predisposes to compression of vital structures including the trachea and great vessels[
3,
4]. Common presenting symptoms can include cough, orthopnoea and respiratory distress, which may initially lead to misdiagnosed infections and a delayed definitive diagnosis[
2].
Prompt imaging facilitates rapid assessment. While CT is an excellent imaging modality to delineate significant anatomical structures and assist with surgical or biopsy planning. Even in this particular case, the images demonstrated tracheobronchial compression with resultant lung collapse necessitating airway protection[
3,
4]. In children, multidisciplinary support for anaesthetic induction in these cases is paramount to avoid a catastrophic outcome of airway collapse.
Histological diagnosis of YSTs is based on the presence of Schiller-Duval bodies within the background and elevated serum AFP level[
5,
6]. The patient in this case had elevated serum AFP, which confirmed the histological diagnosis and acted as an indicator of treatment response. Immunohistochemical markers, such as glypican-3 and SALL4, can be helpful in supporting the identification of YST, but were not used in this particular case[
6].
Chemotherapy is the cornerstone of treatment. The BEP regimen has shown activity in mediastinal germ cell tumours and expectations of outcome are based on tumour burden, AFP level and initial response[
4,
5,
10]. Our patient showed early regression of tumour with a shortening of his AFP level to the extent that he was minimally symptomatic and had minimal toxicity in this high-risk situation—which previous data would lend towards this being an excellent response.
Surgical resection is not indicated in acute presentations and is only considered as an option when there is a persistent or refractory mass after chemotherapy or some evidence of residual viable tumour[
7]; our patient’s tumour responded well enough to medical therapy, and subsequent surgical options were postponed.
Prognostically a mediastinal location is considered poorer than a gonadal location[
1,
4,
10]. However, commencing chemotherapy early, in this stressful case, allowed for clearance of a life-threatening disease. Recent prospective cohort studies suggest that tumour size > 5 cm, and poor early AFP clearance, may be negative prognostic factors[
10]. Longitudinal measurement of AFP and imaging is fundamental.
Importantly, this case has highlighted the tremendous role that the intensive care unit, oncology, anaesthesia, and psychosocial teams have in supporting the child’s recovery. Not only did the child benefit from biopsychosocial interventions from a biomedical perspective, he benefited from his family’s daily presence and consistent psychosocial counselling, reflecting the holistic model of pediatric oncology care[
8,
9].
Possible late effects of BEP might include nephrotoxicity, ototoxicity, and pulmonary fibrosis (Table 3). Our patient will have long-term follow-up that entails audiologic, renal, and pulmonary evaluations as part of survivorship care[
11]. Reintegration into age-appropriate development and education will be prioritized after recovery.
Conclusion
This report highlights that prompt multidisplinary action, namely airway management and starting systemic therapy can significantly improve the outcomes of paediatric mediastinal yolk sac tumours, whereas ongoing psychosocial support is also vital to the care of these patients and their families.
The Author(s) 2026. This article is published with open access at journal.hep.com.cn.
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