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...

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 h...

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