Abstract

Objective

Omental involvement is critically important for staging and prognosis, especially in ovarian and endometrial carcinomas. However, current recommendations regarding the optimal extent of histopathological sampling in grossly normal-appearing omentum are largely practice-based and vary widely. The aim of this study was to evaluate the impact of omental sampling extent on the detection of microscopic metastases in a large cohort of ovarian and endometrial carcinomas and to provide concrete evidence to the literature.

Methods

This retrospective study reviewed gynecologic oncology specimens from 1098 patients (1071 with a carcinoma and 27 with a serous borderline tumor) treated at our department between 2014 and 2023. Cases were evaluated for age, primary tumor location, histologic subtype, chemotherapy status, presence of a microscopically detected (occult) omental focus (<0.5 cm) and of macroscopic disease, the number of blocks sampled, and the block number in which the focus was first detected.

Results

Of 1098 cases, 723 (65.8%) showed no omental metastasis, 329 (30%) had obvious/macrometastasis, and 46 (4.2%) had micrometastasis. Among micrometastasis cases, 43 (93.5%) were high-grade tumors and 3 (6.5%) were borderline. The percentage of micrometastasis detection in the first cassette was 52.2%, and 26.1% in the second cassette. The mean cassette number for first micrometastasis detection was 1.87. Statistical analysis using bootstrapping with 10,000 iterations determined the probability of detecting micrometastasis in any single cassette as 53.9%. Cumulative analysis showed that this rate increased proportionally with cassette number: 95.5% detection with 4 cassettes and 99.6% with 7 cassettes. When examined by primary site, the mean first detection cassette was 2.2 for endometrial cancers and 1.78 for tubo-ovarian carcinomas, with no significant difference between the two tumor locations (Mann-Whitney U test, p=0.495).

Conclusions

In conclusion, a greater extent of omental sampling is associated with improved detection of microscopic metastases. Our data suggest that sampling at least four tissue blocks from grossly normal-appearing omentum achieves >95% sensitivity, providing an optimal balance between diagnostic yield and practical workflow considerations.

Keywords: Omentum, micrometastasis, sampling, tubo-ovarian carcinoma, endometrial carcinoma, diagnostic sensitivity

# Abstract {.unnumbered} ```{r setup-functions} #| include: false # Source manuscript functions source("./R/manuscript_functions.R") source("./R/data_for_manuscript.R") ``` ## Objective Omental involvement is critically important for staging and prognosis, especially in ovarian and endometrial carcinomas. However, current recommendations regarding the optimal extent of histopathological sampling in grossly normal-appearing omentum are largely practice-based and vary widely. The aim of this study was to evaluate the impact of omental sampling extent on the detection of microscopic metastases in a large cohort of ovarian and endometrial carcinomas and to provide concrete evidence to the literature. ## Methods This retrospective study reviewed gynecologic oncology specimens from `r cohort_stats$n_total` patients (`r cohort_stats$n_total - grade_stats$n_borderline` with a carcinoma and `r grade_stats$n_borderline` with a serous borderline tumor) treated at our department between 2014 and 2023. Cases were evaluated for age, primary tumor location, histologic subtype, chemotherapy status, presence of a microscopically detected (occult) omental focus (<0.5 cm) and of macroscopic disease, the number of blocks sampled, and the block number in which the focus was first detected. ## Results Of `r cohort_stats$n_total` cases, `r metastasis_stats$n_no_tumor` (`r metastasis_stats$pct_no_tumor`%) showed no omental metastasis, `r metastasis_stats$n_macro` (`r metastasis_stats$pct_macro`%) had obvious/macrometastasis, and `r metastasis_stats$n_micro_only` (`r metastasis_stats$pct_micro_only`%) had micrometastasis. Among micrometastasis cases, `r micro_stats$n_micro_high_grade` (`r micro_stats$pct_micro_high_grade`%) were high-grade tumors and `r micro_stats$n_micro_borderline` (`r micro_stats$pct_micro_borderline`%) were borderline. The percentage of micrometastasis detection in the first cassette was `r detection_stats$pct_first_cassette`%, and `r detection_stats$pct_second_cassette`% in the second cassette. The mean cassette number for first micrometastasis detection was `r detection_stats$mean_first_detection`. Statistical analysis using bootstrapping with 10,000 iterations determined the probability of detecting micrometastasis in any single cassette as `r boot_results$pct_q`%. Cumulative analysis showed that this rate increased proportionally with cassette number: `r cumulative_detection$cumulative_pct[4]`% detection with 4 cassettes and `r cumulative_detection$cumulative_pct[7]`% with 7 cassettes. When examined by primary site, the mean first detection cassette was `r location_comparison$mean_endo` for endometrial cancers and `r location_comparison$mean_ovary` for tubo-ovarian carcinomas, with no significant difference between the two tumor locations (Mann-Whitney U test, p=`r location_comparison$wilcox_p_formatted`). ## Conclusions In conclusion, a greater extent of omental sampling is associated with improved detection of microscopic metastases. Our data suggest that sampling at least four tissue blocks from grossly normal-appearing omentum achieves >95% sensitivity, providing an optimal balance between diagnostic yield and practical workflow considerations. **Keywords:** Omentum, micrometastasis, sampling, tubo-ovarian carcinoma, endometrial carcinoma, diagnostic sensitivity