Detection and quantification of microplastics in various types of human tumor tissues

Microplastics (MPs) have been detected in various human tissues. However, whether MPs can accumulate within tumors and how they affect the tumor immune microenvironment (TIME) and therapeutic responses remains unclear. This study aimed to determine the presence of MPs in tumors and their potential effects on the TIME. Sixty-one tumor samples were collected for analysis. The presence of MPs in tumors was qualitatively and quantitatively assessed using pyrolysis-gas chromatography-mass spectrometry. MPs were detected in 26 of the samples examined. Three types of MPs were identified: polystyrene, polyvinyl chloride, and polyethylene. In lung, gastric, colorectal, and cervical tumors, the MP detection rates were 80 %, 40 %, 50 %, and 17 % (7.1-545.9 ng/g), respectively. MPs were detected in 70 % of pancreatic tumors (18.4-427.1 ng/g) but not detected in esophageal tumors. In pancreatic cancer, the MP-infiltrated TIME exhibited a reduction in CD8⁺ T, natural killer, and dendritic cell counts, accompanied by substantial neutrophil infiltration. This study illustrates the potential presence of MPs in diverse tumors; varying adhesive affinities were observed among different tumor types. MPs may lead to a more adverse TIME in pancreatic tumors. Further investigations are warranted to assess whether MPs promote tumor progression and affect the efficacy of immunotherapy.