Can Pneumocystis jirovecii colonize lung tumors? New insights from multi-site screening in lung cancer patients

A new study published in Frontiers in Cellular and Infection Microbiology investigates whether the opportunistic fungal pathogen Pneumocystis jirovecii can colonize lung tumor tissue.

Researchers of our COST Action CA23142 analysed multiple sample types (including neoplastic lung tissue, normal adjacent tissue, and respiratory secretions) from 70 patients with primary lung cancer using molecular detection and genotyping approaches. Pneumocystis jirovecii DNA was detected in 11.4% of patients, including cases where the organism was identified directly in tumour tissue.

Although tumour tissue did not appear to be a preferential niche, the findings suggest that tumour-associated microenvironmental factors, particularly in high-grade adenocarcinomas, may influence fungal colonization. These results highlight the potential role of the lung microbiome and mycobiome in the context of cancer biology.

Why this study matters

This research contributes to a growing body of evidence linking microorganisms to cancer biology.

The results suggest that:

• Opportunistic fungi such as Pneumocystis jirovecii may be present within the lung tumour microenvironment.
• Tumour-associated immune and inflammatory changes may influence pathogen colonization.
• Multi-specimen screening approaches may be important to accurately detect Pneumocystis colonization.

These findings support further investigation of the lung microbiome as a potential biomarker and modulator of tumour-associated processes.

Article reference

Magdalena Szydłowicz, Zaneta Zajaczkowska, Mariusz Chabowski, Maciej Nowicki, Błazej Łukianowski, Pawel Gajdzis, Martin Kvac, Enrique J. Calderon, Solène Le Gal, and Marta Kicia.

Multi-site screening for Pneumocystis jirovecii in lung cancer: possible tumour tissue colonization (2026).

Frontiers in Cellular and Infection Microbiology

DOI: 10.3389/fcimb.2026.1755638