Ectopic decidua

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Ectopic decidua
Other names: Deciduosis, decidualized endometriosis[1]
SymptomsNo symptoms[1]
ComplicationsUsually none[2]
Usual onsetPregnancy[1]
Risk factorsPregnancy, progestin use, trophoblastic disease, hormone producing ovarian lesions outside the ovary[2]
Differential diagnosisLuteinized sex cord stromal tumor, cancer spread from skin or lung.[2]
FrequencyAll pregnancies[1]

Ectopic decidua is the presence of decidual cells outside the uterus, typically in pregnancy.[1] Generally there are no symptoms, and it is usually detected when investigating another problem.[1] There may be a tummy ache if the appendix is involved.[2]

It may be associated with trophoblastic disease, ovarian lesions outside the ovary that produce hormones, or the use of progestin.[2] In pregnancy, sites of involvement include the appendix, inner cervix, uterus, fallopian tubes, bowel, bladder and omentum.[2] Under the microscope, it may appear as a single nodule or a cluster of small nodules just under the peritoneal surface.[3] If the lesion is large enough to be seen by direct visualisation, it may be mistaken for a cancer.[2] It tends to resolve without significant complications after delivery of the baby.[2] Other conditions that may appear similar include luteinized sex cord stromal tumor, and cancer spread from skin or lung.[2]

It is most commonly seen during pregnancy; microscopically in all pregnancies and macroscopically in up to 10% of pregnancies.[1] This condition was first described in 1971 by Walker[4] and the name 'ectopic decidua' was coined by Tausig.[5]


  1. 1.0 1.1 1.2 1.3 1.4 1.5 1.6 WHO Classification of Tumours Editorial Board, ed. (2020). "3. Tumours of the peritoneum: Ectopic decidua". Female genital tumours: WHO Classification of Tumours. Vol. 4 (5th ed.). Lyon (France): International Agency for Research on Cancer. p. 206. ISBN 978-92-832-4504-9. Archived from the original on 2022-06-17. Retrieved 2022-07-30.
  2. 2.0 2.1 2.2 2.3 2.4 2.5 2.6 2.7 2.8 Suster, David; Liu, Martina Z.; Lin, Douglas I. (2019). "3. Benign diseases of the ovary". In Zheng, Wenxin; Fadare, Oluwole; Quick, Charles Matthew; Shen, Danhua; Guo, Donghui (eds.). Gynecologic and Obstetric Pathology. Vol. 2. Springer: Springer. pp. 89–90. ISBN 978-981-13-3018-6. Archived from the original on 2022-08-01. Retrieved 2022-07-30.
  3. Gilks, C. Blake (2019). "7. Peritoneum: Benign Mullein lesions". In Nucci, Marisa R.; Oliva, Esther (eds.). Diagnostic Pathology: Gynecological (2nd ed.). Philadelphia: Elsevier Health Sciences. p. 267. ISBN 978-0-323-54815-1. Archived from the original on 2022-08-01. Retrieved 2022-07-30.
  4. Bolat, Filiz (2012). "Pregnancy related peritoneal ectopic decidua: Morphological and clinical evaluation". Turkish Journal of Pathology. 28 (1): 56–60. doi:10.5146/tjpath.2012.01098. PMID 22207433.
  5. Ober, William (1957). "Ectopic ovarian decidua without pregnancy". American Journal of Pathology. 33 (2): 199–217. PMC 1934629. PMID 13402883.