Biochemical Heterogeneity of Endometriosis Phenotypes Revealed by <scp>FTIR</scp> Analysis

Fourier-transform infrared (FTIR) spectroscopy was used to investigate molecular differences among peritoneal, ovarian, bowel endometriosis phenotypes and control tissues. Peritoneal lesions showed the most pronounced spectral changes in CH-stretching (2800-3000 cm^-1) and 1000-1500 cm^-1 regions, indicating protein and lipid alterations. Bowel lesions exhibited moderate but significant deviations, particularly in protein- and nucleic acid-associated bands, while ovarian lesions displayed subtler differences with increased lipid-related CH-stretching. Principal component analysis distinguished all phenotypes from controls, with peritoneal clustering most distinct, bowel intermediate, and ovarian partially overlapping. Key discriminative regions included phosphate vibrations (1080-1100, 1240-1250 cm^-1), CH₂ bending (~1450 cm^-1), amide I (~1650 cm^-1), and amide II (~1540 cm^-1). Decision tree analysis identified phenotype-specific markers: 988 cm^-1 (ovarian), 1101 cm^-1 (bowel), 1544 cm^-1 (peritoneal). Marker intensity correlated with tumor size and clinical scores, strongest in ovarian lesions. These findings highlight phenotype-specific FTIR fingerprints, offering diagnostic and prognostic potential in endometriosis.