Non-neoplastic cysts / other
Ectopic decidual reaction

Author: Aurelia Busca, M.D., Ph.D. (see Authors page)
Editor: Carlos Parra-Herran, M.D.

Revised: 14 March 2017, last major update February 2017

Copyright: (c) 2003-2017, PathologyOutlines.com, Inc.

PubMed Search: Ectopic decidual reaction
Cite this page: Ectopic decidual reaction. PathologyOutlines.com website. http://www.pathologyoutlines.com/topic/ovarynontumorectopicdecidual.html. Accessed July 16th, 2018.
Definition / general
  • Presence of ectopic decidualized uterine stromal cells in the ovary
  • Ectopic decidua or ovarian deciduosis
  • Often an incidental finding in surgical specimens or discrete nodule / mass discovered during caesarean section
Radiology description
Case reports
  • Benign entity, no further treatment necessary; usually regresses 4 - 6 weeks postpartum
  • If mass forming and imaging shows worrisome features for malignancy, the lesion is excised to establish the correct diagnosis
Gross images

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Ectopic decidual reaction

Microscopic (histologic) description
  • Large polygonal cells with abundant eosinophilic cytoplasm, bland nuclei and visible nucleoli
Microscopic (histologic) images

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Left decidualized ovarian mass

Negative stains
Differential diagnosis
  • Endometriosis, which can also undergo decidualization during pregnancy
  • Epithelial ovarian neoplasm when mass forming
  • Peritoneal mesothelioma or peritoneal carcinomatosis when there is additional involvement of peritoneal surface
Additional references