Rojas-Zapata, T

Abstract Introduction The diagnosis of fungal lung infections remains challenging as standard tests, such as bronchoalveolar lavage (BAL) antigen testing, often yield variable or inconclusive results. These limitations can delay appropriate therapy and may require additional tissue sampling for definitive diagnosis. Robotic-assisted bronchoscopy (RAB) biopsy has been primarily used as a minimally invasive technique for assessing suspicious peripheral pulmonary lesions (PPL). This case series highlights the diagnostic utility of RAB for identifying fungal infections within PPL when conventional BAL antigen analysis is non-diagnostic. Case Description Four patients with suspected infectious or malignant PPL underwent RAB-guided biopsy for diagnostic clarification, all yielding histopathologic confirmation of fungal disease. The first, a 73-year-old bilateral lung-transplant recipient with hemoptysis, had a negative BAL Aspergillus antigen despite RAB biopsy confirming Aspergillus infection. Similarly, a second 73-year-old man with chronic obstructive pulmonary disease (COPD) and esophageal adenocarcinoma had a negative BAL antigen, while RAB biopsy of bilateral cavitary lesions confirmed Aspergillus. Additionally, a 39-year-old woman with a nodule being evaluated for malignancy, had negative BAL Histoplasma antigen and PCR, whereas RAB biopsy confirmed Histoplasma capsulatum. In contrast, a 56-year-old woman with a right-lower-lobe nodule had a positive BAL Aspergillus antigen that aligned with the histopathologic biopsy findings. Discussion BAL-based antigen testing demonstrates variable diagnostic accuracy in fungal lung disease. Reported sensitivities for Aspergillus detection are typically high in meta-analysis, approximately 80%-90%, but clinical performance in the immunocompromised or high-risk patients is often substantially lower. Similarly, while BAL antigen testing for Histoplasma performs well in disseminated infections, it often fails to detect localized pulmonary disease. In this series, three out of four patients had negative BAL results in the presence of histopathologic confirmation of fungal infection. While current guidelines consider BAL positivity supportive of a “probable” diagnosis, tissue histopathology remains the gold standard for a “proven” infection. These findings emphasize the value and capability of RAB in obtaining direct tissue confirmation when conventional testing, such as BAL antigen analysis, is non-diagnostic. Conclusion RAB-guided biopsy of PPLs offers the opportunity for histopathologic confirmation of fungal infection when BAL testing is non-diagnostic. This approach can enhance upfront diagnostic yield in patients with suspected fungal pulmonary infections, avoiding delays in diagnosis and treatment initiation. This abstract is funded by: None