Genetic analysis for mucinous ovarian carcinoma with infiltrative and expansile invasion and mucinous borderline tumor: a retrospective analysis

BACKGROUND: Mucinous carcinoma (MC) is a histological subtype of ovarian cancer that has a worse prognosis at advanced stages than the most prevalent histological subtype, high-grade serous carcinomas. Invasive patterns have been recognized as prognostic factors for MCs. MCs with infiltrative invasion were more aggressive than those with expansile invasion. MC with an expansile pattern exhibited behavior similar to mucinous borderline tumors (MBT). However, genomic analysis of invasive patterns is insufficient. This study aimed to compare genetic information between groups with MC and infiltrative invasion (Group A) and those with MC with expansile invasion or MBT (Group B). METHODS: Ten cases each of MC with infiltrative invasion, MC with expansile invasion, and MBT between 2005 and 2020 were identified. Deoxyribonucleic acid (DNA) extraction from formalin-fixed paraffin-embedded tissues was performed, and cases with DNA fragmentation or the possibility of DNA fragmentation were excluded. Mutant base candidates and tumor mutation burden (TMB) values (mutations/megabase) were calculated. RESULTS: After assessing the quality of purified DNA, seven cases of MC with infiltrative invasion, five cases of MC with expansile invasion, and three cases of MBT were included. More patients in group A experienced recurrence or progression (p < 0.01) and died of disease (p = 0.03). Moreover, the TMB value was statistically higher in group A than in group B (p = 0.049). There were no statistical differences in the incidence of the mutations of KRAS, TP53, and CREBBP. KRAS, TP53, and CREBBP mutations were discovered in 8/15 (53.3%), 6/15 (40.0%), and 5/15 (33.3%) cases, respectively. CONCLUSIONS: Genetic analysis revealed that Group A had higher TMB than Group B. Therefore, this result might be useful for future treatment.