Adenomyosis associated with endometrial cancer: Possible correlation with pathological, immunohistochemical and molecular characteristics

BACKGROUND/OBJECTIVE: Adenomyosis is a benign uterine disorder characterized by an inflammatory and hyperestrogenic state. Its association with endometrial cancer (EC) remains controversial. This study aimed to investigate the correlation between adenomyosis and the pathological, immunohistochemical (IHC), and molecular features of EC. METHODS: This retrospective cohort study analyzed 172 patients with EC who underwent surgical staging. Patients were stratified into two groups based on the presence of adenomyosis. The primary endpoint was the prevalence of FIGO stage ≥IB disease. Secondary endpoints included tumor histotype, grade, lymphovascular invasion, IHC markers, and molecular alterations. Logistic regression was performed to identify independent predictors of adverse pathological features. RESULTS: Adenomyosis was identified in 37.2 % of EC patients. These patients were younger, less likely to be postmenopausal, and exhibited significantly lower rates of FIGO stage ≥IB disease, deep myometrial invasion, lymphovascular invasion, and extrauterine spread. Multivariate analysis confirmed adenomyosis as an independent protective factor against FIGO stage ≥IB disease. This protective effect could be attributed to the altered myometrial microenvironment in adenomyosis, characterized by inflammation, smooth muscle hyperplasia, and fibrosis, which appears to limit tumor invasiveness. No significant differences were observed in IHC or molecular profiles, although a trend toward higher prevalence of KRAS mutations was observed in patients with adenomyosis. CONCLUSION: Adenomyosis was associated with a lower prevalence of FIGO stage ≥IB disease, deep myometrial invasion, lymphovascular invasion, and extrauterine spread. These findings suggest that structural changes in the myometrial microenvironment may play a role in limiting tumor invasiveness and spread, warranting further investigation.