# Multi-site screening for Pneumocystis jirovecii in lung cancer: possible tumour tissue colonization

## TL;DR

This study explores whether the fungus Pneumocystis jirovecii can colonize lung cancer tissue, finding it in some tumor and adjacent tissues, suggesting a possible link to cancer progression.

## Contribution

The study is the first to report Pneumocystis jirovecii colonization in lung tumor tissue, highlighting its potential as a biomarker in lung cancer.

## Key findings

- Pneumocystis jirovecii was detected in 11.4% of lung cancer patients across multiple tissue types.
- Two patients had Pneumocystis in all three specimen types, with a statistically significant association to high-grade malignancy.
- Genotype distribution varied across sample types, indicating possible tumor-related influences on colonization.

## Abstract

Recent studies suggest that various tumour types can be colonized by different microorganisms, but data on unusual opportunistic fungus – Pneumocystis jirovecii – remain scarce. Lung cancer patients are considered one of the risk groups for its infection. Since P. jirovecii tends to distribute focally within the lungs, this study aimed to determine whether it can be detected in lung tumour tissue.

Fragments of neoplastic tissue (NPL), normal adjacent tissue (NAT) and respiratory secretions (RS) were collected from 70 patients with histologically confirmed primary lung cancer. DNA was extracted and analysed by nested-PCR targeting the mtLSU rRNA and CYB loci, followed by genotyping.

Pneumocystis jirovecii was detected in fourteen samples derived from 8/70 individuals (11.4%): two NPL, six NAT and six RS. In two patients, Pneumocystis was detected in all three specimen types; both were diagnosed with the same histological malignancy grade (G3, P=0.036). The genotype distribution varied across sample types in most cases.

The ability of Pneumocystis to colonize NPL may be linked to the stage of tumour advancement, suggesting that local tumour-related factors could influence its colonization. These findings support further investigation of the lung microbiome in the context of tumour-associated microenvironments and their potential utility as complementary biomarkers in lung cancer.