Improving Diagnostic Yield in Peritoneal Endometriosis: Value of Additional Level Sections and Sampling Protocols

To evaluate whether deeper histologic sections and tissue-blocking practices improve the diagnosis of endometriosis in peritoneal biopsies. We retrospectively reviewed 148 peritoneal biopsy cases with clinical suspicion of endometriosis from June 1, 2024 to April 1, 2025. Cases with incidental findings, unrelated surgeries, or mass-forming lesions without peritoneal sampling were excluded. We analyzed the influence of block number per biopsy site and the use of additional histologic level sections on diagnostic yield. Associations with surgical approach and reporting pathologist were also assessed. Across all biopsies, detection of endometriosis increased with submission of more tissue blocks per biopsy site: 60% (1 block), 74% (2 blocks), and 86% (≥3 blocks) (P=0.00048). However, this effect did not persist in within-patient comparisons, suggesting confounding by extent of disease. Additional histologic levels were ordered in 32.5% of cases and were associated with increased detection in otherwise negative cases (P=0.039). No significant association was found between the level of use and the number of biopsies per patient or blocks per site. Surgeons with endometriosis subspecialty training had significantly higher diagnostic yields (P=0.0008), as did patients with more biopsy sites sampled (P=0.0009). Among pathologists, diagnostic yield ranged from 59% to 91% (P=0.014), and yield was not explained by usage of level sections. More biopsy sites (extent of disease), submission of more tissue blocks per site, and additional levels improve pathology diagnosis in surgery for peritoneal endometriosis. Variation among surgeons and pathologists underscores the need for standardized protocols and collaborative approaches to optimize histologic confirmation.