title: Decidualization of ovarian endometriosis during pregnancy mimicking malignancy.
abstract: OBJECTIVE
  The purpose of this series is to present deciduosis (the formation of extrauterine decidua) as one of the differential diagnoses of a malignant tumor during pregnancy.
  
  
  METHODS
  Two cases are described in which pregnant patients had a pelvic tumor. The lesions, which were diagnosed in the early second trimester, consisted of complex masses with an extensive blood supply and had a sonographic appearance of a malignant tumor. The high suspicion for malignancy necessitated surgical intervention.
  
  
  RESULTS
  During surgery, the lesions were observed to be of an ovarian origin with papillary excrescences covering their exterior. The lesions were excised and sent for histologic examination. The results showed a markedly decidualized endometriotic cyst in both cases.
  
  
  CONCLUSIONS
  This phenomenon is a diagnostic challenge and should be considered in the differential diagnosis of a malignant mass during pregnancy.
authors.affiliation: Department of Obstetrics and Gynecology, Bnai-Zion Medical Center, PO Box 4940, Haifa 31048, Israel.
authors.forename: Rami N
authors.initials: RN
authors.lastname: Sammour
authors.forename: Zvi
authors.initials: Z
authors.lastname: Leibovitz
authors.forename: Israel
authors.initials: I
authors.lastname: Shapiro
authors.forename: Shimon
authors.initials: S
authors.lastname: Degani
authors.forename: Zohar
authors.initials: Z
authors.lastname: Levitan
authors.forename: Ariel
authors.initials: A
authors.lastname: Aharoni
authors.forename: Joseph
authors.initials: J
authors.lastname: Tal
authors.forename: Michael
authors.initials: M
authors.lastname: Lurie
authors.forename: Gonen
authors.initials: G
authors.lastname: Ohel
mesh_terms: D000328:Adult; D003656:Decidua / Q000000981:diagnostic imaging* / Q000473:pathology / Q000601:surgery; D003937:Diagnosis, Differential; D004715:Endometriosis / Q000000981:diagnostic imaging* / Q000473:pathology / Q000601:surgery; D005260:Female; D006801:Humans; D010535:Laparoscopy; D010051:Ovarian Neoplasms / Q000000981:diagnostic imaging* / Q000473:pathology / Q000601:surgery; D011247:Pregnancy; D011256:Pregnancy Outcome; D011262:Pregnancy Trimester, Second; D014463:Ultrasonography