Clinical Medicine Only EBUS-Guided Mediastinal Lymph Node Cryobiopsy Enabled Immunotherapy in a Patient with Non-Small Cell Lung Cancer

Mutational analysis and programmed death ligand 1 (PD-L1) expression are required for personalized treatment of metastatic non-small cell lung cancer (NSCLC). The detection of a targetable driver mutation has prognostic and predictive relevance, giving the patient the opportunity to receive highly effective first line targeted treatment with a kinase inhibitor. The better tolerability of these oral medications in comparison to platinum-doublet chemotherapy and immunotherapy often allows for treatment of frail patients or in the context of relevant comorbidities. In the absence of a targetable driver mutation or a contraindication to immunotherapy, the choice of first line treatment for patients with NSCLC depends on PD-L1 expression. For patients with PD-L1 ≥ 50%, Pembrolizumab or Cemiplimab monotherapy is standard of care, while platinum-based doublet chemotherapy should be added to Pembrolizumab or Atezolizumab in cases where PD-L1 < 50%. Therefore, precise molecular and immunohistochemical characterization of metastatic NSCLC should be pursued with maximal effort. Tissue sampling is affected by size and/or localization of tumour lesions, which may result in insufficient biopsy samples, both in terms of quantity and quality. In cases of mediastinal or hilar lymph node involvement, cytological specimens obtained by EBUS-TBNA can often confirm malignancy, but cytological samples with low cellularity may not always be suitable for precise immunocytochemical and molecular tumour characterization. Endobronchial and transbronchial cryobiopsy can yield large tissue samples allowing exact tumour characterization and may be superior to other biopsy techniques. EBUS-TBLNC is a technically challenging diagnostic procedure requiring extensive endoscopic expertise and has only been reported in individual cases and first case series. The authors describe a patient in whom several attempts of characterization of a lung tumour by different sampling techniques (pleural puncture, transthoracic lung biopsy, EBUS-TBNA) were unsuccessful due to low cellularity. Only EBUS-TBLNC yielded sufficient tumour material for detailed immunohistochemical and molecular characterization and allowed determination of the optimal systemic therapy for non-squamous NSCLC.

Case report of an 83-year-old male former smoker (30 pack-years), ECOG PS 1, with multiple comorbidities. Initial work-up for symptomatic left pleural effusion revealed a left lower lobe lung lesion with lymphangiosis and discrete hilar/mediastinal lymphadenopathy. Pleural drainage cytology showed single TTF-1–positive pulmonary adenocarcinoma cells, but material was insufficient for molecular analysis. EBUS-TBNA of mediastinal lymph node station 4L (four passes, each 8–10 needle passes) yielded representative samples by rapid on-site evaluation but no malignant cells were present. Subsequent CT-guided transthoracic biopsy again yielded too few tumour cells for DNA/RNA extraction for NGS. Mediastinoscopy was declined due to increased perioperative risk and patient preference. Liquid biopsy was considered unlikely to be informative given low systemic tumour burden. Given these constraints, EBUS-guided transbronchial lymph node cryobiopsy (EBUS-TBLNC) was performed after informed consent discussing limited experience and potential risks. Under EBUS guidance, a monopolar electric needle knife was used to tunnel through the bronchial wall towards LN 4L. A 1.1 mm cryoprobe was introduced through the incision into the lymph node. After 7 seconds of freezing, several biopsies were extracted in succession, with a combined specimen size of approximately 0.8 × 0.7 × 0.4 cm. No bleeding or other acute/delayed peri-interventional complications were observed. Pathology showed extensive infiltrates of TTF-1–positive adenocarcinoma. Comprehensive profiling included NGS, immunohistochemistry, and FISH. Results demonstrated a pathogenic TP53 mutation in exon 8, no actionable genetic alterations, and PD-L1 expression with 100% tumour cell membranous staining by Ventana SP263 assay. Based on these findings and risk–benefit assessment, first-line Pembrolizumab monotherapy was initiated.

- Multiple standard sampling attempts (pleural fluid cytology, EBUS-TBNA of LN 4L with four aspirates and 8–10 passes each, CT-guided transthoracic biopsy) failed to provide sufficient material for molecular testing. - EBUS-TBLNC successfully obtained solid lymph node tissue (combined size ~0.8 × 0.7 × 0.4 cm) without complications after a 7-second freeze using a 1.1 mm cryoprobe via transbronchial tunneling with an electric needle knife. - Histology: Extensive TTF-1–positive adenocarcinoma infiltrates. - Molecular/IHC/FISH: Pathogenic TP53 mutation in exon 8; no actionable/targetable genetic alterations detected; PD-L1 expression positive in 100% of tumour cells (Ventana SP263). - Treatment decision: Enabled initiation of PD-1–directed immunotherapy (Pembrolizumab monotherapy) as first-line therapy. - Clinical course: Due to intercurrent, non–tumour-related medical issues and decline to ECOG PS 3, immunotherapy was discontinued; the patient died of tumour progression five months after the first and only dose. Tumour response to therapy is unknown as no further assessments were performed.

This case demonstrates that EBUS-guided transbronchial lymph node cryobiopsy (EBUS-TBLNC) can overcome limitations of conventional sampling methods by providing larger, higher-quality tissue suitable for comprehensive molecular and immunohistochemical profiling in NSCLC. After pleural cytology, EBUS-TBNA, and CT-guided biopsy all proved inadequate for molecular workup due to low cellularity or absence of malignant cells, EBUS-TBLNC enabled full characterization, including confirmation of absent actionable mutations and high PD-L1 expression, directly informing first-line treatment selection. Although technically demanding and with limited reported experience, EBUS-TBLNC may be a valuable addition to the diagnostic armamentarium for mediastinal lymph node involvement when standard methods are insufficient, facilitating personalized therapy decisions.

Only EBUS-guided mediastinal lymph node cryobiopsy provided adequate tumour tissue for complete histo-molecular characterization in this patient with non-squamous NSCLC, revealing PD-L1 expression in 100% of tumour cells without actionable mutations and enabling initiation of immunotherapy. This case underscores the importance of selecting biopsy techniques capable of yielding sufficient, high-quality specimens to guide personalized treatment in NSCLC, particularly when conventional sampling is inadequate.

- Single-patient case report limits generalizability. - EBUS-TBLNC is technically challenging with limited clinical experience reported. - The patient’s intercurrent medical issues led to discontinuation of therapy and lack of subsequent tumour assessments; hence, treatment response to Pembrolizumab is unknown. - Mediastinoscopy was not performed, and liquid biopsy was not pursued due to low expected yield, which may limit comparative assessment of alternative diagnostic strategies.