1. Russells Hall Hospital, Dudley, West Midlands. UK
A case of peritoneal deciduosis discovered during a cesarean section
Dr.Hashem Elhossamy, MRCOG - Specialty Doctor
Mr.Hassan Morsi, FRCOG, MSC, MD.Consultant of Obstetrics and Gynaecology
Russells Hall Hospital, Dudley, West Midlands. UK
Background
Discussion continued
Decidual cell groups outside the endometrium are named “ectopic decidua” or “deciduosis” and this condition has first been defined by Walker in
Ectopic decidua is most commonly localized in the ovary, cervix and uterine serosa 2 while the peritoneal localization is rare, It generally has no clinical symptoms.3
Most ectopic decidua cases are related to normal pregnancy as in our case post operatively.
The origin of peritoneal deciduosis has been a debated subject with the proposal of two possible theories. The first is that the sub-coelomic mesenchymal cells undergo a progesterone-induced metaplasia whereas the second theory claims that the decidual cells are already distributed in the peritoneum, e.g. from preexisting endometriosis.5
Ectopic decidua is a common occurrence during pregnancy, corresponding to the presence of decidual tissue outside the endometrium. The pathophysiology of these lesions is not yet fully elucidated. The phenomenon is most often benign, with a favourable outcome in the post-partum and without follow-up. Because of the wide range of clinical presentations, from localized peritoneal granulation to large pelvic mass, the clinical diagnosis of ectopic decidua is difficult. Furthermore, imaging is not specific. The discovery of such lesions should lead to the realization of systematic biopsies for histological examination and rule out other causes such as lesions of tuberculosis or carcinomatosis. Immunohistochemical studies are helpful in differentiating deciduosis from malignant deciduoid mesothelioma, its main differential diagnosis with a catastrophic prognosis.6
Peritoneal deciduosis regresses within the 4-6 weeks duration after pregnancy with decidual involution. It therefore requires no therapeutic intervention and disappears without complication in the postpartum period Peritoneal ectopic decidua is found incidentally in biopsies obtained during a cesarean section, tubal pregnancy, elective tubal ligation and appendectomy.7
A case was reported of ectopic peritoneal and omental deciduosis of the peritoneum and discovered incidentally during caesarean section. Definitive diagnosis was done by immunohistological examination. A laparoscopy four months later showed complete and spontaneous regression of all lesions.8
Another case of a 27 year old G1P0 female with a dichorionic, diamniotic twin pregnancy presenting with premature rupture of membranes found to have omental caking and diffuse yellow-tan peritoneal nodules, clinically suspicious for carcinomatosis. The case work-up showed this to be an example of florid-diffuse peritoneal deciduosis mimicking carcinomatosis which has since resolved 4 months postpartum.9
Case
A 32 years old lady, primigravida, no previous medical or surgical history had an uneventful pregnancy. Dating and anatomy scan at 20 weeks showed no abnormality and a posterior placenta. Patient then presented in labour at 39 weeks, a breech presentation was suspected and confirmed by abdominal ultrasound scan. An emergency cesarean section was performed.
A soon as peritoneum was breached a blood stained serous fluid was seen within abdominal cavity, the anterior surface of the uterus showed numerous tortuous blood vessels and after delivery of the baby and closing the uterus a 10 cm diameter haemorrhagic left adnexal mass with uterine vessels / merging over the anterior uterus to utero vesical  pouch was identified. A biopsy was taken from this mass.
Histopathology 
Macroscopic report:
Three irregular soft tissue pieces received, two of which are congested, altogether measuring 35 x 30 x 20mm.
Microscopic report:
The sections show few fragments of decidual tissue along with blood. There is an occasional fragment containing smooth muscle cells with decidual sheets infiltrating within it. There are no obvious chorionic villi or trophoblastic tissue seen. There is no evidence of atypia or malignancy.    
References and Contact
Discussion
1- Walker A: Der Bau der Eihaeute bei Graviditatis abdominalis. Virchows Arch Path Anat 1887, 197:72-99
2- Schneider V, Barnes LA: Ectopic decidual reaction of the uterine cervix: frequency and cytologic presentation. Acta Cytol 1981, 25:
3- Shukla S, Pujani M, Singh SK: Ectopic decidual reaction mimicking peritoneal tubercles: a report of three cases. Indian J Pathol Microbiol 2008, 51:
4- Barbieri M, Somigliana E, Oneda S, Ossola MW, Acaia B, Fedele L. Decidualized ovarian endometriosis in pregnancy: a challenging diagnostic entity. Hum Reprod. 2009;24:1818–1824.
5- Zaytsev P, Taxy JB. Pregnancy-associated ectopic decidua. Am J Surg Pathol. 1987;11:526–530.
6- Canlorbe G, Goubin-Versini I, Azria E, Abdul-Razak R, Muray JM. [Ectopic decidua: variability of presentation in pregnancy and differential diagnoses]. Gynecol Obstet Fertil Apr;40(4):
7- Büttner A, Bässler R, Theele C: Pregnancy-associated ectopic decidua (deciduosis) of the greater omentum. An analysis of 60 biopsies with cases of fibrosing deciduosis and leiomyomatosis peritonealis disseminata. Pathol Res Pract 1993, 189:
8- Abramowicz S, Kouteich K, Grémain J, Sabourin JC, Marpeau L, Sergent F. [Giant ectopic peritoneal and omental deciduosis mimicking a peritoneal carcinomatosis]. Gynecol Obstet Fertil Mar;42(3): Adhikari LJ, Shen R. Florid diffuse peritoneal deciduosis mimicking carcinomatosis in a primigravida patient: a case report and review of the literature. Int J Clin Exp Pathol Oct 15;6(11):
Correspondence author:
Decidualization is the hypertrophy of endometrial stromal cells by the effect of progesterone. Similarly, in pregnancy, ectopic stromal endometrial cells in endometriosis can also be transformed by the same mechanism and ectopic decidua (deciduosis) may occur. 4
Ectopic decidual reaction of the peritoneum and the omentum is rare. It is usually an incidental finding during caesarean section and it could mimic macroscopically peritoneal carcinomatosis or tuberculosis. Histology is very important to make diagnosis. Ectopic decidual reaction is physiological, with an excellent prognosis and spontaneous resolution.4
Adnexal masses complicating pregnancy have been reported to occur in average 1 in 600 of live births and approximately 11% of these are endometriomas. These decidual changes of endometriosis can be characterized by mural nodules and that macroscopically mimics a malignant tumor. Therefore, in literature, there are several reported cases and all of them have resulted in surgery during pregnancy because of the suspicious imaging findings.4