Case of atypical polypoid adenomyoma that possibly underwent a serial progression from endometrial hyperplasia to carcinoma

Atypical polypoid adenomyoma is a rare uterine tumor composed of atypical endometrial glands, which often exhibit squamous metaplasia, and a cellular smooth muscle stroma. Although atypical polypoid adenomyoma is categorized as a benign lesion, it is reportedly associated with endometrial cancer, and it shows persistence and recurrence even after conservative medical treatment. We present a rare case of atypical polypoid adenomyoma that possibly underwent a serial pathological change from endometrial hyperplasia to carcinoma in a 40‐year‐old woman with no history of pregnancy. She was diagnosed with atypical polypoid adenomyoma during polypectomy surgery. After resecting the atypical polypoid adenomyoma, endometrial hyperplasia complex was detected. This condition eventually progressed from atypical hyperplasia complex to endometrial adenocarcinoma, and total abdominal hysterectomy was performed. A patient with atypical polypoid adenomyoma who wishes to preserve her fertility should be carefully monitored for endometrial carcinoma. If endometrial hyperplasia is detected in such a patient, a meticulous follow‐up examination by performing endometrial biopsy is mandatory.