Exuberant Ectopic Decidualization : A Case Report

Problem Statement: Ectopic decidual transformation (or deciduosis) is a benign transient condition of pregnancy that arises from a progesterone-induced metaplasia of subserosal stromal cells. It is commonly localised in the pelvic organs serosa while the peritoneal localisation is less frequent and usually an incidental finding during caesarean section. However, decidualized tissue can grow during pregnancy and acquire a gross appearance that might mimic more serious conditions. A biopsy is necessary for establishing the diagnosis and to exclude the presence of mesothelioma, metastatic carcinoma, or peritoneal tuberculosis. We hereby report a case of extensive ectopic decidualization of the anterior surface of the uterus, discovered incidentally during a caesarean section performed due to fetal distress.Methods: A retrospective study of a clinical case of extensive ectopic decidualization of the uterus serosa at the Maternidade Dr. Alfredo da Costa in Lisbon, Portugal.Case Description: A 35-year-old primiparous woman with a medical past of endometriosis and an uneventful antenatal period underwent a caesarean section at term due to fetal distress. Upon delivery, the anterior uterine serosa showed an exuberant dark-red exophytic lesion, with an irregular and highly friable surface and well-defined borders, which was biopsied. Further examination of the abdominal cavity revealed no other lesions. Mother and infant were discharged from hospital on the third postoperative day without any postpartum complications.The microscopic examination of all biopsy fragments revealed similar histomorphological aspects, consistent with the diagnosis of ectopic decidual transformation.Conclusion: Ectopic decidua is usually found incidentally during surgery and is most commonly described in the pelvic organs serosa. Although a benign lesion that resolves with no treatment in the postpartum period, it can demonstrate an uncommon presentation and mimic more serious conditions, like a malignant growth. A histological analysis with immunohistochemistry are necessary for the diagnosis in these cases.