2 Introduction
Omental involvement is one of the fundamental factors determining staging, prognosis, and treatment decisions, particularly in ovarian and endometrial carcinomas. In endometrial carcinoma, the presence of omental metastasis is associated with significantly decreased overall survival and classifies the disease as FIGO stage IVB. Additionally, omental involvement correlates with other adverse clinicopathologic features including deep myometrial invasion, high tumor grade, non-endometrioid histology, lymph node metastasis, and adnexal involvement. Therefore, accurate detection of omental disease, including microscopic metastases, is of great clinical importance.
In tubo-ovarian carcinoma, the omentum is a frequent site of metastasis. The observation that removal of macroscopically involved omentum results in better clinical outcomes led to omentectomy becoming a routine part of surgical staging procedures in the 1960s1. Although the precise biological role of the omentum in tumor dissemination has not been fully elucidated, the presence of occult omental metastases even in apparently early-stage disease has historically justified the inclusion of omentectomy in surgery for accurate staging2. However, the extent of pathologic sampling required to reliably detect microscopic omental involvement remains controversial.
In this study we use the term microscopically detected (occult) omental metastasis to denote a metastatic focus that is not identified on gross examination or palpation and is found only on histologic review; for a reproducible size criterion we defined such a focus as measuring less than 0.5 cm. We avoid the term “micrometastasis” because in gynecologic pathology it carries a distinct, size-specific meaning in the context of lymph node staging, and applying it to omental deposits could cause confusion. The 0.5-cm threshold was chosen pragmatically, as it approximates the lower limit of what can be reliably appreciated on gross inspection and palpation of the omentum; foci below it are, in practice, the ones that depend on histologic sampling for detection. We did not test alternative thresholds, and the cutoff is intended as an operational definition of grossly occult disease rather than a biologically derived boundary.
Current guidelines and practice-based recommendations show marked variation regarding omental sampling. When grossly evident tumor is present, limited representative sampling is generally considered adequate. In contrast, for grossly normal-appearing omentum, recommended block numbers vary widely, ranging from two to four blocks based on current practice3 to five to ten blocks in certain pathology protocols4. However, these recommendations are largely based on expert opinion or limited model studies rather than robust outcome-based evidence. Indeed, one model study demonstrated that examination of five omental blocks yielded 82% sensitivity in detecting microscopic metastases, while increasing the block number to ten raised sensitivity to approximately 95%5. These findings clearly illustrate the potential impact of sampling extent on diagnostic sensitivity.
Conflicting data exist in the literature regarding the adequacy of omental sampling. Some large retrospective series have suggested that submission of one or two blocks from the omentum does not significantly reduce metastasis detection rates compared to more extensive sampling6,7. In contrast, studies specifically examining staging-negative and macroscopically normal omentum have emphasized that limited sampling may miss microscopic disease8. Furthermore, the more limited sampling recommended for patients receiving neoadjuvant chemotherapy (four to six blocks) is primarily aimed at assessing treatment response and does not target maximal sensitivity for detecting microscopic metastases. This reflects the heterogeneity of clinical contexts in which omental sampling is performed.
The significant prognostic importance of microscopic omental involvement, particularly in high-risk endometrial carcinomas, combined with the lack of clear consensus in the literature regarding omental sampling, highlights the need for studies based on real-world data. In this study, we retrospectively evaluated the relationship between omental sampling extent and detection of microscopic metastases in a large cohort of patients with ovarian and endometrial carcinoma.