Isolated Squamous Morular Metaplasia of the Endometrium in the Absence of Proliferative Pathology: A Case Report and Review of the Literature

Isolated squamous morular metaplasia is an uncommon histopathologic finding in the endometrium that most frequently occurs in association with endometrioid proliferative lesions, including endometrial hyperplasia, endometrial intraepithelial neoplasia, and endometrioid adenocarcinoma. Squamous morular metaplasia in the absence of proliferative pathology is rare, and its clinical significance and optimal management remain poorly defined. A 43-year-old nulliparous woman presented with abnormal uterine bleeding. Her medical history was significant for morbid obesity and early menarche. Endometrial biopsy demonstrated focal squamous morule formation without evidence of endometrial hyperplasia or malignancy. A levonorgestrel-releasing intrauterine device was placed for the management of abnormal uterine bleeding and reduction of endometrial hyperplasia risk. Repeat endometrial biopsy revealed inactive-pattern endometrium, confirming stability with conservative progestin therapy. Studies have reported an association with isolated squamous morular metaplasia and subsequent endometrioid carcinoma and Wnt/β-catenin pathway dysregulation, supporting the need for clinical monitoring. In patients with significant risk factors for unopposed estrogen exposure, isolated morules may represent a marker of an endometrium predisposed to future proliferative changes. Isolated squamous morular metaplasia is an uncommon diagnosis that may warrant clinical surveillance due to its association with endometrioid carcinoma. Progestin-based therapy may provide a reasonable management strategy while allowing continued monitoring. Additional research is needed to clarify the prognostic value of morular metaplasia and the role of immunohistochemical evaluation in guiding follow-up strategies.