Microplastic accumulation in paired human breast tumor and para-tumor tissues and exploratory clinical associations.

Microplastics (MPs) are emerging environmental contaminants. However, their occurrence in human breast tissues and clinical relevance remain largely unexplored. In this exploratory study, MPs were characterized in paired tumor and para-tumor tissues from seven breast cancer patients using laser direct infrared (LDIR) spectroscopy, with selected particles further examined by scanning electron microscopy. Across all samples, 26 polymer types were identified. Chlorinated polyethylene (CPE) was detected in all samples and was the most abundant polymer, alongside polyurethane (PU), fluororubber (FKM), and fluorosilicone rubber (FSR). Total MP abundance tended to be higher in tumor tissues than in para-tumor tissues, although differences were not statistically significant (p = 0.0663, paired t test, Cohen's d = 0.85). The predominance of hydrophobic polymers, together with the lipid-rich composition of breast tissue, may favor passive retention of MPs, contributing to tissue-specific distribution patterns. Exploratory analyses suggested potential associations between PU abundance, clinicopathological features (including Her-2 expression), and lifestyle factors such as padded brassiere use. Given the limited sample size, these findings are hypothesis-generating. This study provides a detailed polymer-level characterization of MPs in paired human breast tissues, offering initial insights into tissue-specific distribution.