Biochemical Heterogeneity of Endometriosis Phenotypes Revealed by FTIR 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 ), CH 2 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.