ABSTRACT
Squamous metaplasia may be associated with endometrial hyperplasia or carcinoma, but is also sometimes associated with endometritis or chronic pyometra. Mucinous metaplasia occurs in perimenopausal or postmenopausal women and it may be associated with hormone replacement therapy. Mucinous metaplasia is commonly found in tamoxifen-associated endometrial polyps. Adenomyomatous polyp is a benign lesion composed of endometrial glands surrounded by endometrial stroma and smooth muscle. Atypical polypoid adenomyoma was traditionally regarded as a benign lesion although it was well documented that some cases were associated with coexisting endometrial hyperplasia or malignancy. A number of benign lesions or metaplastic changes can arise in the endometrium, many of them potentially resembling malignant neoplasms due to morphologic overlap and variations. Endometrial stromal nodules are rare benign mesenchymal tumors of endometrial stromal differentiation. Lesions expressing sex cord markers are best regarded as uterine tumor resembling ovarian sex cord tumors, while those expressing smooth-muscle markers and negative for sex cord markers could be reported as plexiform tumorlets.
