A Deceptive Spread: Myoinvasion of Endometrial Carcinoma Imitating Adenoma Malignum

Endometrioid type of endometrial carcinoma is the most common form of uterine malignancy. The majority of patients in the developed world present with the low-grade, low-stage type of this malignancy. The current treatment of early-stage endometrioid carcinoma provides most patients with a favorable outcome. One of the important factors that determine the outcome of early-stage endometrial carcinoma is the involvement of cervical stroma. One of the very rare forms of cervical stromal involvement by endometrioid carcinoma is termed "adenoma malignum type" invasion due to its similarity to the infamously deceptive type of cervical adenocarcinoma called adenoma malignum. Since adenoma malignum is often discovered incidentally, finding adenoma malignum type of myoinvasion may deceive a pathologist to diagnose the simultaneous presence of endometrial carcinoma and adenoma malignum in the same patient as 2 separate entities. Also, this type of myoinvasion may be missed altogether for its subtle nature. In this article, we report a case of low-grade, low-stage endometrioid carcinoma with adenoma malignum type of myoinvasion. We have pointed out the subtle nature of this lesion and the important features to remember to successfully identify it.