Multi-site screening for Pneumocystis jirovecii in lung cancer: possible tumour tissue colonization
Members of the COST Action CA23142 – Delve into Pneumocystis network have published a new study in Frontiers in Cellular and Infection Microbiology exploring the presence of Pneumocystis jirovecii in lung cancer patients. This study provides evidence that the opportunistic fungus Pneumocystis jirovecii can occasionally be detected within lung tumour tissue, suggesting that tumour-associated microenvironmental changes may facilitate microbial colonization.
Understanding how microorganisms interact with cancer tissues is an emerging field in biomedical research. While bacteria and viruses have been extensively studied in this context, much less is known about the role of opportunistic fungi such as Pneumocystis jirovecii.
In this study, researchers investigated whether P. jirovecii, a fungal pathogen commonly associated with pneumonia in immunocompromised individuals, can also be detected directly within lung tumour tissue. Lung cancer patients are known to be at increased risk of Pneumocystis infection or colonization, but its presence within tumour tissue itself has rarely been explored.
To address this question, biological samples were collected from 70 patients with primary lung cancer during surgical procedures. Three different types of specimens were analysed: neoplastic lung tissue, adjacent non-tumour lung tissue, and respiratory secretions. Molecular detection was performed using nested PCR targeting mitochondrial genetic markers commonly used for Pneumocystis identification and genotyping.
The results showed that Pneumocystis jirovecii DNA was detected in 11.4% of patients. In two cases, the fungus was identified directly in tumour tissue, and in both patients it was also detected in surrounding lung tissue and respiratory secretions. These findings indicate that while tumour tissue does not appear to be the primary niche for the organism, Pneumocystis may occasionally colonize the tumour microenvironment.
Interestingly, the presence of Pneumocystis in tumour tissue was observed only in patients with high-grade lung adenocarcinoma, suggesting that more advanced tumours may create local conditions that facilitate opportunistic microbial colonization. Changes in the tumour microenvironment (such as altered immune responses, inflammation, and tissue remodeling) may influence the distribution of microorganisms within the lungs.
Although the study does not demonstrate that Pneumocystis contributes directly to tumour development, the results highlight the importance of exploring the lung microbiome and mycobiome in cancer biology. Microorganisms present in tumour-associated tissues could potentially serve as biomarkers of disease progression or provide new insights into the complex interactions between infections, inflammation, and cancer.
Overall, this work contributes to a growing body of research investigating the relationship between microbes and cancer, and supports further studies on the role of respiratory microorganisms in the lung tumour microenvironment.
Article reference
Authors: Magdalena Szydłowicz, Zaneta Zajaczkowska, Mariusz Chabowski, Maciej Nowicki, Błazej Łukianowski, Pawel Gajdzis, Martin Kvac, Enrique J. Calderon, Solène Le Gal, and Marta Kicia.
Title: Multi-site screening for Pneumocystis jirovecii in lung cancer: possible tumour tissue colonization (2026).
Journal: Frontiers in Cellular and Infection Microbiology
DOI: 10.3389/fcimb.2026.1755638
