Abstract
BACKGROUND: Endometrial cancer arising in adenomyosis (EC-AIA) is a rare entity of endometrial cancer, and its clinical significance has not been well studied. This study aimed to examine the tumor characteristics and survival outcomes of EC-AIA. METHODS: An exploratory analysis was performed to compare EC-AIA and historical control cases. For this study, EC-AIA cases were identified via a systematic literature search using PubMed/MEDLINE with entry keywords "endometrial cancer OR uterine cancer" AND "adenomyosis" (n = 46). The control group comprised consecutive non-EC-AIA cases from four institutions that had hysterectomy-based surgical staging (n = 1294). Patient demographics, pathology results, and survival outcomes were evaluated between the two groups. RESULTS: The EC-AIA group was significantly older than the control group (58.9 vs. 55.3 years; P = 0.032). In terms of tumor characteristics, 56.5% of the EC-AIA cases showed tumor within the myometrium without endometrial extension, and the EC-AIA group was significantly more likely to have tumors with more than 50% myometrial invasion (51.6 vs. 26.6%; P = 0.002) and serous/clear cell histology (22.2 vs. 8.2%, P = 0.002) while less likely to express estrogen receptor (14.3 vs. 84.6%; P < 0.001). Grade and stage distributions were similar (P > 0.05). In the univariate analysis, the EC-AIA group had a significantly poorer disease-free survival than the control group (5-year rate: 71.4 vs. 80.6%; P = 0.014). In the multivariate analysis, with control for age, ethnicity, histology, grade, and stage, EA-CIC remained an independent prognostic factor for decreased disease-free survival (adjusted hazard ratio, 3.07; 95% confidence interval 1.55-6.08; P = 0.001). CONCLUSIONS: The study suggested that endometrial cancer arising in adenomyosis may be an aggressive variant of endometrial cancer.