Survival outcomes of expansile versus infiltrative subtype in primary mucinous ovarian carcinomas: A retrospective study in Thailand

OBJECTIVE: To compare the prognostic outcomes of the expansile and infiltrative subtypes of primary mucinous ovarian carcinoma (PMOC). METHODS: This retrospective cohort study involved patients with PMOC who underwent surgery between 2018 and 2023. All specimens were re-evaluated by an expert pathologist according to the 2020 WHO classification and categorized as expansile or infiltrative subtypes. Overall survival (OS) and progression-free survival (PFS) were evaluated using Kaplan-Meier analysis. Univariate and multivariate Cox regression analyses were performed to identify independent factors associated with OS and PFS. RESULTS: Among 65 cases of PMOC, 38 (58.5%) were classified as expansile and 27 (41.5%) as infiltrative. The median follow-up duration was 33 (range, 1-86 months). Five-year OS and PFS rates did not differ significantly between the two subtypes (79.2% vs. 73.5%, P = 0.37; 82.5% vs. 79.2%, P = 0.40; respectively). In multivariate analysis, the invasion pattern was not an independent prognostic factor; instead, advanced stage (hazard ratio [HR], 5.10; 95% confidence interval [CI]: 1.06-24.55; P = 0.04) and residual tumor ≥1 cm (HR 11.26, 95% CI: 1.11-114.21; P = 0.04) were independently associated with worse PFS. For overall survival, only residual tumor ≥1 cm remained an independent adverse prognostic factor (HR 37.17, 95% CI: 2.71-510.07; P = 0.007). CONCLUSION: Pathologic subtype was not independently associated with survival after adjustment for stage and residual disease; however, the limited sample size and low number of outcome events may have reduced the ability to detect clinically meaningful differences. Stage and residual disease were the dominant prognostic factors.