Pediatric Cryptococcosis Presenting as a Mediastinal Mass: A Case Report And Endobronchial Ultrasound-Guided Transbronchial Needle Aspiration Protocol

Summary

This visualized case report presents a clinical protocol for performing endobronchial ultrasound-guided transbronchial needle aspiration via a laryngeal mask airway to support the diagnosis of pulmonary cryptococcosis presenting as an unexpected mediastinal mass in an immunocompetent pediatric patient.

Abstract

Endobronchial ultrasound-guided transbronchial needle aspiration (EBUS-TBNA) is a minimally invasive diagnostic technique. While widely used in adults, its application for diagnosing mediastinal masses in pediatric patients remains underreported. This gap poses challenges when addressing atypical presentations, such as pulmonary cryptococcosis in immunocompetent children, which is frequently misdiagnosed due to nonspecific symptoms. We present the case of a healthy nine-year-old male with an eight-day history of fever and cough. Computed tomography revealed a mediastinal mass in the left hilum and a mass in the left lower lobe. Following unsuccessful empirical antibiotic therapy, further invasive investigation was warranted. This article describes an EBUS-TBNA protocol tailored for pediatric patients. The procedure was performed using total intravenous anesthesia and a laryngeal mask airway. An ultrasound bronchoscope was advanced, and Doppler imaging was used to confirm the target lymph node's relationship with the surrounding vasculature. In this case, a lesion under the second carina was identified. A 22 G aspiration needle was inserted to a depth of 1–2 cm. Maintaining 5–15 mL of negative pressure, 20–30 rapid agitations were performed to obtain samples. The biopsy samples underwent histopathological examination and next-generation sequencing. The tissue demonstrated positive periodic acid-Schiff and Grocott methenamine silver staining, supporting identification of Cryptococcus spp. Following targeted fluconazole therapy, the patient achieved complete clinical and radiographic recovery. This case illustrates the potential usefulness of EBUS-TBNA in a carefully selected pediatric patient when conventional tests fail.

Introduction

Pulmonary cryptococcosis (PC) is a significant fungal infection caused by the encapsulated yeasts Cryptococcus neoformans and Cryptococcus gattii, which are ubiquitous in environmental reservoirs such as soil and avian excreta¹. Historically characterized as an opportunistic infection primarily affecting immunocompromised individuals, particularly those with HIV/AIDS or patients undergoing prolonged immunosuppressive therapy, recent epidemiological shifts have highlighted a concerning rise in incidence among immunocompetent hosts^2,3. In China, over 50% of PC cases now occur in patients without identifiable risk factors, and approximately 60% of HIV-negative patients with PC lack any underlying comorbidities^2,4.

In the pediatric population, PC remains a rare clinical entity, which often leads to a low index of suspicion among healthcare providers³. Unlike adults, who may present with distinct pulmonary nodules, children frequently exhibit non-specific symptoms such as persistent fever, cough, and chest pain, or they may even remain entirely asymptomatic until the disease is advanced^2,5. This lack of characteristic clinical features poses a substantial diagnostic challenge, often resulting in delayed treatment and an increased risk of dissemination to the central nervous system (CNS)^1,3. The initial presentation in pediatric cases can easily be misidentified as bacterial pneumonia, tuberculosis, or even malignancy, necessitating more invasive diagnostic strategies when initial empirical treatments fail^2,4.

The radiographic manifestation of PC in children further complicates the diagnostic pathway. While peripheral pulmonary nodules are the most common finding, mediastinal lymphadenopathy and mass-like lesions are increasingly reported in pediatric series^5,6. In some cases, a prominent mediastinal mass may be the primary finding, mimicking lymphoma, sarcoidosis, or miliary tuberculosis^5,7. Standard laboratory confirmation, including serum cryptococcal capsular polysaccharide antigen (CrAg) testing and sputum cultures, often yields negative results in localized pulmonary disease or early-stage pediatric infections, as observed in the present case^2,4. Therefore, obtaining high-quality tissue specimens for histopathological confirmation is the definitive method for diagnosis^6,8.

Endobronchial ultrasound-guided transbronchial needle aspiration (EBUS-TBNA) has emerged as a valuable, minimally invasive tool for evaluating mediastinal and hilar lymphadenopathy⁷. While its efficacy and safety are well-established in adult thoracic oncology, its application in pediatrics is a more recent development requiring specialized protocols^7,8. EBUS-TBNA allows for real-time visualization of lesions and precise vascular mapping via Doppler ultrasound, which is critical in the narrower pediatric airway to minimize the risk of accidental vascular injury^6,8. Recent meta-analyses confirm that EBUS-TBNA provides a high diagnostic yield for pediatric mediastinal pathology, ranging from 76% to 81%, making it a safer alternative to more invasive procedures like mediastinoscopy or open biopsy^7,8.

To optimize the safety and success of EBUS-TBNA in children, specific anesthetic and airway management strategies must be employed. The use of a laryngeal mask airway (LMA) in conjunction with total intravenous anesthesia (TIVA) offers a stable and secure airway while providing the bronchoscopist with sufficient space to manipulate the ultrasound probe⁹. Evidence suggests that LMA-based protocols in children result in fewer perioperative complications compared to traditional endotracheal intubation⁹. Furthermore, the integration of metagenomic next-generation sequencing (mNGS) with EBUS-obtained samples has facilitated the detection of atypical pathogens, such as Cryptococcus spp., particularly when conventional cultures remain negative^4,10.

This article presents a visualized protocol for diagnosing pulmonary cryptococcosis in an immunocompetent 9-year-old child who presented with an atypical mediastinal mass. The patient had no known exposure to avian species or pigeon droppings, an unremarkable family and medical history, and normal immunological evaluations, including normal lymphocyte subpopulations and immunoglobulin levels. By detailing the multidisciplinary workflow, including TIVA/LMA-based anesthesia, real-time ultrasound-guided aspiration, and the application of mNGS for rapid pathogen identification, this protocol provides a practical approach for evaluating selected complex pediatric thoracic lesions. The successful resolution of this case following targeted fluconazole therapy illustrates the potential role of EBUS-TBNA as a diagnostic option in pediatric respiratory medicine¹.

Case Presentation:

A previously healthy nine-year-old male was admitted with an eight-day history of persistent fever (peaking at 39.5 °C) and a non-productive cough. Physical examination and initial laboratory tests were unremarkable. However, chest computed tomography (CT) revealed a 2.6 cm x 2.5 cm mass in the left hilum alongside an additional mass in the left lower lobe. The patient initially received two weeks of empirical intravenous antibiotic therapy, but clinical symptoms persisted, and follow-up imaging showed no reduction in the size of the masses.

Given the risk of malignancy or atypical infection, a multidisciplinary team (MDT) determined that a tissue diagnosis was essential. The patient was scheduled for endobronchial ultrasound-guided transbronchial needle aspiration (EBUS-TBNA). The procedure was performed under total intravenous anesthesia (TIVA) using a size 3 laryngeal mask airway (LMA) to ensure stable ventilation. Using an ultrasound bronchoscope, the operator first performed a routine bronchoscopic inspection, which identified a significant obstruction in the basal segment of the left lower lobe. Subsequent real-time ultrasonic scanning identified a heterogeneous, enlarged lymph node located under the second carina. Under continuous ultrasound guidance and after using Doppler imaging to confirm the absence of intervening blood vessels, a 22 G aspiration needle was advanced into the lesion. Multiple aspirates were collected and submitted for histopathological examination and metagenomic next-generation sequencing (mNGS).

Diagnosis, Assessment, and Plan:
Diagnosis: Isolated pulmonary cryptococcosis presenting as a mediastinal mass in an immunocompetent pediatric patient.

Assessment: The primary clinical challenge was the atypical presentation of pulmonary cryptococcosis as a prominent mediastinal mass in a healthy child, a scenario that frequently mimics lymphoma or tuberculosis. The clinical priority was to obtain definitive tissue samples while minimizing the trauma of a surgical biopsy in a pediatric patient. EBUS-TBNA via LMA was selected as a less invasive approach with reported diagnostic utility for pediatric mediastinal lesions. The integration of mNGS with traditional histopathology was helpful because traditional cultures may remain negative for Cryptococcus in early-stage or localized disease, whereas mNGS provided rapid molecular identification of the pathogen. Concurrently, Grocott methenamine silver (GMS) and periodic acid-Schiff (PAS) staining confirmed the presence of encapsulated fungal yeasts within the tissue.

Plan: Following the confirmation of Cryptococcus spp. through positive staining and mNGS results, the patient was initiated on a targeted antifungal regimen after central nervous system (CNS) MRI and lumbar puncture yielded normal findings, including normal cerebrospinal fluid parameters, negative India ink staining, and absence of cryptococcal antigen in the CSF. These findings showed no evidence of CNS involvement.

(1) Pharmacotherapy: The patient was started on intravenous fluconazole at a dose of 400 mg once daily for seven days, followed by continuous oral administration of fluconazole capsules at 400 mg once daily. The intended duration of oral therapy was six months, with monitoring for adverse effects such as hepatotoxicity. (2) Follow-up: A monitoring plan was established, including chest CT scans at one-month and four-month intervals. These follow-ups were designed to document the gradual resolution of the mediastinal and pulmonary masses and to assess the response to targeted antifungal therapy.

Protocol

This protocol was conducted in accordance with the Declaration of Helsinki and approved by the Ethics Committee of The Children’s Hospital, Zhejiang University School of Medicine, National Clinical Research Center for Children and Adolescents' Health and Diseases (Approval No. 2026-IRB-0151). Written informed consent was obtained from the patient's parent or legal guardian for both the procedure and the publication of this case report, including any identifiable clinical images.

1. Preprocedural evaluation and preparation

1. Preprocedural chest computed tomography (CT) scans were reviewed to identify and select the target mediastinal/hilar lymph nodes and lung masses.
2. A comprehensive preanesthesia assessment was performed. The patient’s adherence to strict preoperative fasting guidelines was confirmed: 2 h for light/clear liquids, 4 h for breast milk, 6 h for formula or starch-based solid foods, and 8 h for fat-based solid foods. Intravenous infusion of glucose-containing fluids was initiated 2 h after fasting began to prevent hypoglycemia and dehydration.
3. Bleeding risk was evaluated by confirming acceptable platelet counts and coagulation profiles before the procedure. In this case, the preoperative evaluation showed a prothrombin time (PT) of 12.0 s, an activated partial thromboplastin time (APTT) of 25.8 s, an international normalized ratio (INR) of 1.05, and a platelet count of 445 × 10⁹/L.
4. Emergency airway backup equipment, including an appropriately sized endotracheal tube and a rigid bronchoscope, was prepared in the operating room.

2. Patient preparation and anesthesia

1. The nine-year-old male patient was placed in the supine position on the procedure table, with the shoulders slightly elevated and the head positioned straight. Intravenous access was established, and standard multi-parameter monitoring was initiated.
2. Total intravenous anesthesia (TIVA) was administered using an intravenous injection of propofol (1.0 mg/kg) and a continuous infusion of remifentanil (0.2 µg∙kg^-1∙min^-1) to ensure a deep level of sedation and patient comfort.
3. A size 3 laryngeal mask airway (LMA) was inserted to maintain a secure and stable airway throughout the interventional procedure, and proper placement was confirmed.
4. A solution of 1% lidocaine was applied topically via surface spray to suppress the cough reflex and optimize procedural conditions. Specifically, 1 mL was administered to the glottis and 2 mL was administered intratracheally.

3. Initial bronchoscopic inspection and bronchoalveolar lavage

1. A 4.2-mm outer diameter flexible diagnostic bronchoscope was introduced through the LMA. A systematic inspection of the airway was performed, including observation of the vocal cords, tracheal position, cartilage rings, and carina.
2. Abnormalities observed during this survey were noted. In this case, significant hyperemia, edema, and excessive white secretions were observed and cleared by suction. External compression narrowing was visualized at the opening of the left lingular bronchus, preventing the 4.2-mm bronchoscope from passing distally.
3. Bronchoalveolar lavage (BAL) was performed at the target bronchus. The bronchoscope was wedged into the target segment, and 37 °C normal saline was instilled at 1 mL/kg per instillation, up to 20 mL per pass, with a total volume not exceeding 5–10 mL/kg.
4. Bronchoalveolar lavage fluid (BALF) was retrieved using a negative pressure suction setting between 100 and 200 mmHg, while avoiding collapse of the bronchial lumen. A fluid recovery rate of ≥40% was achieved, and the samples were collected in non-adhesive sterile containers, such as silicone-coated or polypropylene containers, for microbiological analysis.

4. Endobronchial ultrasound-guided scanning

1. The diagnostic bronchoscope was withdrawn, and an ultrasound bronchoscope equipped with a convex transducer was advanced through the LMA.
2. The ultrasound probe was positioned against the bronchial wall at the level of the second carina to scan for the target lesion.
3. Real-time ultrasonic imaging was used to identify the enlarged, heterogeneous lymph node at the target site. Power Doppler mode was used to visualize and map the surrounding vasculature, ensuring that the intended puncture pathway was free of major blood vessels.

5. Transbronchial needle aspiration

1. Once the target lesion was clearly identified and the vascular relationship was confirmed, a 22 G aspiration needle was introduced through the working channel of the ultrasound bronchoscope.
2. Under continuous real-time ultrasonic guidance, the needle was advanced through the airway wall and into the center of the mediastinal mass to a depth of 1–2 cm.
3. A negative pressure of 5–15 mL was applied using a syringe while the operator performed 20–30 rapid agitations of the needle within the lesion to obtain a core tissue sample.
4. A total of 5 needle passes were performed. In the absence of Rapid On-Site Evaluation (ROSE), sample adequacy was determined by macroscopic visual inspection, with visible tissue cores obtained in all 5 passes.

6. Specimen processing and laboratory analysis

1. The obtained tissue samples were expressed from the needle and divided for multi-modal diagnostic testing.
2. One portion was fixed in 10% neutral buffered formalin for histopathological examination. This included periodic acid-Schiff (PAS) and Grocott methenamine silver (GMS) staining to specifically screen for fungal elements.
3. A second portion was placed in a sterile container and immediately submitted for metagenomic next-generation sequencing (mNGS).
4. The patient was monitored in a recovery unit until the effects of anesthesia had fully subsided.

Results

Table 1 summarizes the patient's clinical characteristics, procedural parameters, and multidisciplinary management timeline. Baseline laboratory evaluations revealed leukocytosis (white blood cell count: 19.32 × 10⁹/L) with neutrophil predominance and an elevated C-reactive protein level of 52.49 mg/L. Organ function tests, tumor markers, and initial infectious disease screenings, including tuberculosis, HIV, and serum cryptococcal antigen testing, were unremarkable. Initial diagnostic imaging was performed via chest computed tomography (CT). The scans revealed a significant mass-like density measuring 2.6 cm × 2.5 cm in the left hilum, alongside an additional mass in the left lower lobe with irregular borders (Figure 1). Furthermore, prominent enlargement of the mediastinal lymph nodes was observed, accompanied by a small volume of pleural effusion (Figure 1). Enhanced CT imaging in the mediastinal window demonstrated heterogeneous enhancement within both the pulmonary nodules and the mediastinal lymph nodes (Figure 2A-D). Follow-up imaging using the lung window showed that the masses remained unchanged after 2 weeks of empirical antibiotic therapy (Figure 2E,F), prompting a more invasive diagnostic approach.

The procedural findings from the endobronchial ultrasound-guided transbronchial needle aspiration (EBUS-TBNA) are visualized in Figure 3. Standard bronchoscopy initially identified a significant luminal obstruction in the basal segment of the left lower lobe bronchus (Figure 3A). Transitioning to real-time ultrasound guidance, a heterogeneous, enlarged lymph node was identified and targeted for aspiration (Figure 3B). Following the successful puncture of the lesion with a 22 G aspiration needle, an immediate release of purulent discharge was observed at the puncture site (Figure 3C). A postprocedural bronchoscopic inspection confirmed that the obstruction in the basal segment of the left lower lobe had significantly improved following the aspiration and clearance of the discharge (Figure 3D).

The definitive diagnosis was established through molecular and histopathological analysis of the obtained tissue. Metagenomic next-generation sequencing (mNGS) of the biopsy samples identified Cryptococcus neoformans, providing a rapid molecular diagnosis. Histopathological examination of the mediastinal lymph node biopsy corroborated these findings. Microscopic analysis showed fungal yeasts characterized by distinct capsules. These elements were clearly highlighted by Grocott methenamine silver (GMS) staining (Figure 4A) and periodic acid-Schiff (PAS) staining (Figure 4B), confirming the presence of encapsulated fungal yeasts consistent with Cryptococcus spp.

The patient’s response to targeted antifungal therapy was monitored through serial CT imaging. Following one month of oral fluconazole treatment, follow-up CT scans demonstrated a significant reduction in the size of the left lower lobe mass and the mediastinal lymphadenopathy (Figure 5A-D). After 4 months of continuous therapy, subsequent imaging showed that the pulmonary mass and mediastinal nodes had essentially resolved and returned to normal physiological dimensions (Figure 5E-H). To evaluate potential dissemination, a central nervous system (CNS) magnetic resonance imaging (MRI) scan and a lumbar puncture were performed, both yielding normal results (normal cerebrospinal fluid biochemistry, negative India ink staining, and an absence of cryptococcal antigen), successfully ruling out CNS involvement. Following the six-month course of antifungal therapy and regular clinical outpatient monitoring, the patient achieved a complete clinical recovery without any drug-related adverse effects or disease recurrence.

Figure 1: Initial chest CT scans identifying the thoracic masses. (A, B) Lung window images demonstrating a mass-like density in the left lower lobe characterized by irregular and spiculated margins. (C, D) Mediastinal window images showing significant enlargement of the mediastinal lymph nodes accompanied by a small volume of pleural effusion. Please click here to view a larger version of this figure.

Figure 2: Preprocedural assessment via enhanced and follow-up CT imaging. (A-D) Enhanced CT images in the mediastinal window showing heterogeneous enhancement within the pulmonary nodules and enlarged mediastinal lymph nodes. (E,F) Follow-up lung window scans showing the persistent left lower lobe mass and stable mediastinal lymphadenopathy following 2 weeks of empirical antibiotic therapy, indicating a lack of response to conventional anti-infective treatment. Please click here to view a larger version of this figure.

Figure 3: Procedural findings during endobronchial ultrasound-guided transbronchial needle aspiration. (A) Bronchoscopic view showing significant luminal obstruction in the basal segment of the left lower lobe bronchus prior to the procedure. (B) Real-time ultrasound image identifying a heterogeneous, enlarged lymph node targeted for aspiration at the second carina. The orange inset displays Power Doppler imaging, which was utilized to map the surrounding vasculature and confirm that the intended puncture pathway was free of major blood vessels. (C) Bronchoscopic view documenting the release of purulent discharge immediately following the puncture of the lesion with an aspiration needle. (D) Postprocedural bronchoscopic view showing the resolution of the airway obstruction and improved ventilation in the left lower lobe segment. Please click here to view a larger version of this figure.

Figure 4: Histopathological confirmation of Cryptococcus spp. in the mediastinal lymph node. (A) Photomicrograph of the biopsy specimen showing fungal yeasts with distinct capsules highlighted by Grocott methenamine silver staining (indicated by arrows). (B) Similar fungal elements highlighted by periodic acid-Schiff staining (indicated by arrows). Original magnification: 40×. Scale bars = 50 µm. Please click here to view a larger version of this figure.

Figure 5: Posttreatment follow-up CT scans demonstrating radiographic resolution. (A-D) CT scans taken 1 month after the initiation of targeted fluconazole therapy, showing a significant reduction in the dimensions of the pulmonary mass and mediastinal lymph nodes. (E-H) Final follow-up CT scans at 4 months post therapy, confirming that the pulmonary and mediastinal lesions have essentially resolved and returned to normal physiological appearance. Please click here to view a larger version of this figure.

Category	Parameter / Description
Patient Demographics & Presentation
Age / Sex	9 years / Male
Clinical Presentation	Fever (up to 39.5 °C), non-productive cough
Symptom Duration	8 days prior to admission
Immune Status	Immunocompetent (HIV-negative, normal lymphocyte subsets and immunoglobulins, no comorbidities)
Baseline Laboratory Findings (New Section)
Blood Tests	Leukocytosis (WBC 19.32 × 109/L, neutrophil predominant); elevated CRP (52.49 mg/L)
Coagulation & Platelets	PT 12.0 s; APTT 25.8 s; INR 1.05; Platelets 445 × 109/L
Infectious Screening	Negative for Tuberculosis, HIV, and initial serum cryptococcal antigen
Diagnostic Imaging & Initial Treatment
Primary Lesions	Left hilar mass (2.6 cm x 2.5 cm) and an additional mass in the left lower lobe
Secondary Findings	Mediastinal lymphadenopathy, minor pleural effusion
Pre-procedural Treatment	2-week empirical intravenous antibiotics (No clinical/radiographic response)
EBUS-TBNA Procedure Parameters
Anesthesia / Airway	Total Intravenous Anesthesia (TIVA) / Size 3 Laryngeal Mask Airway (LMA)
Target Site	Mediastinal lymph node (subcarinal, second carina)
Operative Details	Ultrasound bronchoscope; 22 G aspiration needle; 5 needle passes
Sample Adequacy	Macroscopic visual inspection for intact tissue cores (No Rapid On-Site Evaluation [ROSE])
Procedural Findings	Purulent discharge identified post-puncture; left lower lobe airway obstruction improved
Diagnostic Confirmation & Staging
Histopathology	Encapsulated yeasts identified (PAS and GMS positive)
Molecular Diagnosis	Cryptococcus neoformans detected via mNGS
CNS Assessment	Brain MRI and lumbar puncture normal (negative CSF India ink and cryptococcal antigen)
Treatment & Follow-up Timeline
Pharmacotherapy	Intravenous fluconazole for 7 days, followed by oral fluconazole (400 mg/day) for 6 months
1-month Follow-up	Significant reduction in lesion sizes and lymphadenopathy (CT confirmation)
4-month Follow-up	Essential radiographic resolution
6-month Follow-up	Treatment completed; complete clinical recovery with no adverse effects or disease recurrence

Table 1: Clinical characteristics and diagnostic timeline. This table summarizes the patient's demographic data, initial laboratory findings, procedural parameters of the EBUS-TBNA, and the sequential timeline of the clinical management from admission to the four-month follow-up.

Discussion

The present case described a rare clinical entity: pulmonary cryptococcosis (PC) presenting as an atypical mediastinal mass in an immunocompetent 9-year-old child. The diagnosis was achieved through an endobronchial ultrasound-guided transbronchial needle aspiration (EBUS-TBNA) protocol, providing a minimally invasive alternative to traditional surgical interventions. While Cryptococcus species are typically recognized as opportunistic pathogens in immunocompromised individuals, localized PC in immunocompetent hosts has been increasingly reported, often manifesting with highly non-specific clinical and radiological features¹¹. In such pediatric cases, PC often mimics bacterial pneumonia or tuberculosis, leading to protracted diagnostic delays that can potentially result in systemic dissemination¹². This case illustrates how real-time imaging, specialized pediatric anesthesia, and molecular diagnostics can support evaluation of selected complex pediatric thoracic lesions.

The differential diagnosis of mediastinal masses in children is a substantial clinical challenge. These lesions often necessitate the exclusion of malignancies such as lymphoma, sarcoidosis, or infectious granulomas, including tuberculosis and atypical fungal infections¹³. In the present case, the radiological findings were misleading, demonstrating heterogeneously enhancing mediastinal nodes and a pulmonary mass that were refractory to conventional antibiotic therapy. Standard diagnostic modalities, including sputum cultures and serum cryptococcal antigen testing, frequently exhibit suboptimal sensitivity in localized pediatric cases where the fungal burden is sequestered within the lymph nodes or granulomatous tissue¹⁴. Consequently, EBUS-TBNA was used as a diagnostic tool in this case. Its ability to provide real-time visualization of extraluminal lesions while identifying and avoiding adjacent major vascular structures may be useful in selected pediatric cases^8,15.

Published studies have reported that EBUS-TBNA can be used in pediatric patients to sample mediastinal and hilar lymphadenopathy¹⁵. In this case, the use of a 22 G aspiration needle allowed for the acquisition of sufficient tissue cores for both histopathology and molecular sequencing. The diagnostic yield of EBUS-TBNA for mediastinal pathology in children has been reported to be high, and it may provide a less invasive alternative to procedures such as mediastinoscopy^7,16. The implementation of real-time ultrasound guidance during the puncture was important for identifying the subcarinal lesion while assessing the surrounding pulmonary vasculature, a technical consideration emphasized in initial institutional experiences with EBUS in tuberculosis-endemic populations¹⁶.

The EBUS-TBNA procedure in this patient was supported by specialized anesthetic and airway management. Pediatric interventional bronchoscopy has advanced through refined sedation and airway strategies¹⁷. In this procedure, the use of total intravenous anesthesia (TIVA) combined with a laryngeal mask airway (LMA) established a stable airway while offering the bronchoscopist sufficient operative space to manipulate the ultrasound probe. Compared to traditional endotracheal intubation, the LMA-based approach in pediatric surgeries has been associated with a lower incidence of post-procedural complications, such as laryngospasm and coughing, which may help maintain high-quality ultrasound imaging during aspiration¹⁸. This anesthetic framework provided the stability required for precise needle placement in a confined pediatric thorax, consistent with published studies on airway management^9,18.

Beyond procedural technique, the integration of molecular diagnostics improved the diagnostic utility of the samples obtained in this clinical scenario. Metagenomic next-generation sequencing (mNGS) represents a culture-independent approach that can support identification of fungal pathogens from small-volume biopsy samples¹⁹. In the early stages of infection or in cases with a low fungal load, traditional cultures may require several weeks of incubation and often yield negative results in immunocompetent patients. The application of mNGS to the EBUS-aspirated tissue provided rapid molecular confirmation, facilitating the transition to targeted antifungal therapy²⁰. mNGS has demonstrated diagnostic value for pulmonary infections across various patient populations, providing a faster turnaround time compared to traditional microbiological methods^4,10,21. When combined with histopathological confirmation via Grocott methenamine silver (GMS) and periodic acid-Schiff (PAS) staining, this multi-modal diagnostic approach helped avoid surgical biopsy in this case and guided the long-term antifungal strategy¹.

Despite these positive outcomes, several limitations to this protocol must be acknowledged. First, as a single case report, these findings illustrate a specific clinical scenario and cannot be generalized as definitive proof of the broad safety or effectiveness of this approach. Second, the successful execution of EBUS-TBNA in a pediatric patient requires highly specialized expertise in both pediatric interventional bronchoscopy and pediatric anesthesia, resources that may not be available in all clinical settings. Finally, while mNGS provided rapid pathogen identification in this instance, its high cost and limited diagnostic availability remain significant practical barriers to its routine use in general clinical practice.

In summary, this visualized protocol showed that EBUS-TBNA, when integrated with LMA-based anesthesia and mNGS analysis, provided a minimally invasive diagnostic pathway for this rare mediastinal pathology in a pediatric patient. This multidisciplinary approach supported the time to definitive diagnosis and reduced the need for a traditional surgical biopsy, contributing to clinical resolution in this immunocompetent child with a complex respiratory disease.

Materials

List of materials used in this article

Name	Company	Catalog Number	Comments
1% Lidocaine Hydrochloride Injection	Aspen Pharmacare	NMPA Approval No. H20103516
10% Neutral Buffered Formalin	Sigma-Aldrich	HT501128
22 G Aspiration Needle	Olympus Corporation	NA-201SX-4022
4.2-mm Flexible Diagnostic Bronchoscope	Olympus Corporation	BF-P260F
Endobronchial Ultrasound Bronchoscope	FUJIFILM Corporation	EB-530US
Endoscopic Ultrasound Processor	FUJIFILM Corporation	SU-9000
Grocott Methenamine Silver (GMS) Staining Kit	Cida Biotechnology	CD-GMS-100
Laryngeal Mask Airway (Size 3)	Ambu A/S	Ambu Aura-i, 321300000
Metagenomic Next-Generation Sequencing (mNGS) Service	Shanghai KingMed Diagnostics Co., Ltd.	Custom Service; www.kingmed.com.cn
Multi-parameter Patient Monitor	Mindray Bio-Medical Electronics	cPM 10C
Periodic Acid-Schiff (PAS) Staining Kit	Shaanxi ProAndti Biotechnology Co., Ltd.	PA-0054
Propofol Emulsion for Injection	AstraZeneca	NMPA Approval No. H20010368
Remifentanil Hydrochloride for Injection	Yichang Humanwell Pharmaceutical Co., Ltd.	NMPA Approval No. H20030197