Clinical implications of histologic subtypes on survival outcomes in primary mucinous ovarian carcinoma.

Objective: In 2014, the World Health Organization introduced a new histologic classification by dividing primary mucinous ovarian carcinoma (PMOC) into two: expansile (ES) or infiltrative subtypes (IS). This study investigated the clinical implications of these histological subtypes on survival outcomes.

Methods: Data from 131 patients with PMOC who underwent primary surgery between 2003 and 2021 were analyzed. The patients baseline characteristics, surgical and pathological information were collected. Survival outcomes were calculated, while factors affecting them were also investigated.

Results: During 55.9 months of median follow-up, 27 (20.6%) patients experienced recurrence and 20 (15.3%) died. Among 131 patients, 113 patients were classified into 87 (77%) ES and 26 (23%) IS after a slide review. Advanced stage, lymph node involvement, and residual tumors after surgery were more common in the IS, showing poorer prognosis. In multivariate analyses, advanced stage and residual tumors after surgery were associated with worse survival, while the IS showed no statistical significance. In subgroup analysis for stage I disease, survival did not vary between subtypes. Nevertheless, patients in the IS group who underwent fertility-sparing surgeries demonstrated a 5-year progression-free survival (PFS) rate of 83.3%, significantly lower than patients without fertility preservation, irrespective of histologic subtypes (5-year PFS rate: 97.9%; P = 0.002 for the ES, 5-year PFS rate: 100%; P = 0.001 for the IS).

Conclusions: The IS of PMOC had poorer survival outcomes and a higher proportion of advanced-stage tumors. Although its independent prognostic significance remains uncertain, adjuvant chemotherapy should be considered for patients with fertility preservation in the IS group.