title: Case study of a pregnant woman with decidualized ovarian endometriosis whose preoperative findings suggested malignant transformation.
abstract: BACKGROUND
  Because both decidualization and malignant transformation of endometriosis are characterized by mural nodules on the wall of the cyst, the preoperative differential diagnosis is reportedly difficult.
  
  
  METHODS
  A 31-year-old woman was referred to our hospital at ten weeks of gestation. Sonographic examination revealed an intrauterine gestational sac and ovarian endometrial cyst. At 21 weeks of gestation, characteristic findings associated with malignant transformation of ovarian endometriosis were seen on color-flow Doppler sonography and contrast magnetic resonance imaging. Under the diagnosis of malignant transformation of ovarian endometriosis, right salpingo-oophorectomy was performed at 22 weeks' gestation. However, histopathologic examination revealed ovarian endometriosis with marked decidual changes but no evidence of malignancy.
  
  
  CONCLUSIONS
  During pregnancy, intracystic vascularized excrescences of an endometrial cyst indicate not only malignant transformation but also decidualization. Thus, the preoperative differential diagnosis is reportedly difficult. However, the present findings of decidualization on magnetic resonance imaging seemed to be slightly different from those of malignant transformation, and therefore, might help distinguish decidualized endometriosis from malignant transformation preoperatively.
authors.affiliation: Department of Obstetrics and Gynecology, Yamanashi Red Cross Hospital, Interdisciplinary Graduate School of Medicine and Engineering, University of Yamanashi, Japan.
authors.forename: H
authors.initials: H
authors.lastname: Iwamoto
authors.forename: M
authors.initials: M
authors.lastname: Suzuki
authors.forename: N
authors.initials: N
authors.lastname: Watanabe
authors.forename: M
authors.initials: M
authors.lastname: Minai
authors.forename: S
authors.initials: S
authors.lastname: Hirata
authors.forename: K
authors.initials: K
authors.lastname: Hoshi
mesh_terms: D000328:Adult; D003937:Diagnosis, Differential; D004715:Endometriosis / Q000175:diagnosis* / Q000473:pathology / Q000601:surgery; D005260:Female; D006801:Humans; D010048:Ovarian Cysts / Q000175:diagnosis* / Q000473:pathology / Q000601:surgery; D010049:Ovarian Diseases / Q000175:diagnosis* / Q000473:pathology / Q000601:surgery; D010051:Ovarian Neoplasms / Q000175:diagnosis*; D011247:Pregnancy; D011248:Pregnancy Complications / Q000175:diagnosis* / Q000473:pathology / Q000601:surgery; D011252:Pregnancy Complications, Neoplastic / Q000175:diagnosis