Adenomyosis is a common benign gynecologic lesion which is characterized by abnormal endometrial mucosa in the muscular wall of the uterus. Pathological diagnosis of this condition is generally straightforward but there are few mimicking lesions that a pathologist may be reluctant to make a diagnosis, such as adenomyosis with atrophic and fibrotic
stroma vs well differentiated endometrioid adenocarcinoma with myometrial invasion, adenomyosis with vascular involvement vs. low-grade stromal sarcoma, and cancer arising from adenomyosis or involving adenomyosis. The gynecologic pathologists, gynecologists and gynecologic oncologists should be aware of these mimicking lesions or conditions which may have some problems in diagnosis including the features that have clinical impact upon stage of cancer and treatment.

Keywords: Adenomyosis, Endometrioid adenocarcinoma, Endometrial stromal sarcoma