Incidence of Adenomyosis in Hysterectomy Specimens Performed for Benign Uterine Pathologies: A Six-Year Retrospective Analysis from a Tertiary Center in Romania

Background/Objectives: Adenomyosis is a common yet frequently underdiagnosed cause of gynecological morbidity, and its definitive diagnosis still relies on histopathological examination of hysterectomy specimens. We aimed to determine the histopathological prevalence of adenomyosis in hysterectomy specimens removed for benign indications, characterize preoperative referral diagnoses and concurrent histopathological findings, and compare our results with the contemporary literature. Methods: We retrospectively analyzed 430 consecutive abdominal hysterectomies performed for benign gynecological indications at a tertiary referral center in Iasi, Romania, between January 2019 and October 2024. Adenomyosis was defined histopathologically. An “incidental” finding was defined as the absence of adenomyosis in the preoperative referral diagnosis, without re-review of the original ultrasound reports. We report prevalence and the incidental rate with Wilson-score 95% confidence intervals (CIs); we used the chi-square test with Yates continuity correction for categorical comparisons and calculated odds ratios (ORs), with correction for multiple comparisons. Results: Adenomyosis was identified in 188 of 430 specimens (43.7%; 95% CI 39.1–48.4%), of which 186 (98.9%; 95% CI 96.2–99.7%) were incidental; adenomyosis was recorded in the referral diagnosis in only 2 cases (1.1%). Endometrial hyperplasia was the only co-finding significantly associated with adenomyosis (OR 2.30; 95% CI 1.48–3.55; p = 0.0002), an unadjusted univariate association that remained significant after multiple-comparison adjustment (adjusted p = 0.0014). No referral diagnosis discriminated adenomyosis status; leiomyoma was frequent in both groups (75.5% vs. 69.0%; not significant). Mean age was 50.0 ± 7.6 years, with no between-group difference (p = 0.112). Conclusions: Approximately two in five women undergoing hysterectomy for benign disease have adenomyosis, and it is rarely suspected preoperatively. Because this study did not test whether structured sonographic assessment improves detection, prospective evaluation of the revised 2022 Morphological Uterus Sonographic Assessment (MUSA) criteria with imaging–histopathology correlation is warranted.