Decidualized ovarian and rectouterine deep endometriosis disguised as malignancy in the second-trimester of pregnancy: A case report

A 26-year-old woman at 14 weeks of gestation presented to our hospital for the first time routine examination. TVS detected an intrauterine gestational sac of size 7.1 × 7.0 cm with heartbeat. Besides, three undefined pelvic masses were also detected. There was one cystic mass with size 8.7 × 7.3 cm with weak echo of the capsule in the left ovary, another one same as the former with size 5.5 × 4.8 cm in the right ovary, and the third one with size 3.3 × 3.1 cm in the rectouterine pouch ( Fig. 1 A and B). These masses had never been detected before pregnancy. This patient did not have dysmenorrhea, dyschezia, dysuria, or dyspareunia during menstruation before. It only took this couple two years for this natural pregnancy. To figure out the problem, pelvic MRI without contrast media was conducted. There was an irregular signal intensity lesion of size 3.7 × 2.3cm with isointense on T1-weighted images and hyperintense on T2-weighted images involving the posterior cervical wall. The left adnexal lesion of size 7.8 × 7.4cm with some papillary wall thickening was hyperintense on T1-weighted and T2-weighted images. The right adnexal lesion of size 2.9 × 4.0cm was isointense on T1-weighted images and mixed hyperintense on T2-weighted images with diffusion limited on axial DWI ( Fig. 1 C). Both adnexal masses were reported to be ovarian endometrioid carcinoma with metastasized lesion in the rectouterine pouch. Serum CA125 elevated to 56.7 U/L. HE-4 was 73.9 U/L, with CA199 normal. Fig. 1 Images of decidualized endometriosis in this young pregnant woman. A&B: TVS showed the bilateral cystic ovarian lesions (L&R) with flocculent echo of the inner wall and rectouterine pouch nodular mass with vascularity (yellow circle). C: MRI showed that the right adnexal lesion was hyperintense on T2-weighted images with diffusion limited on axial DWI, thought to be potential malignancy. Fig. 1 Images of decidualized endometriosis in this young pregnant woman. A&B: TVS showed the bilateral cystic ovarian lesions (L&R) with flocculent echo of the inner wall and rectouterine pouch nodular mass with vascularity (yellow circle). C: MRI showed that the right adnexal lesion was hyperintense on T2-weighted images with diffusion limited on axial DWI, thought to be potential malignancy. For this young pregnant woman who was diagnosed with potential bilateral adnexal malignancy with one metastasized lesion, treatment approach was difficult to be decided. MDT with doctors from departments of gynecology, obstetrics, radiology and pathology was arranged at once. After thorough discussion, the decision was made to proceed with surgery to determine the pathology first. Considering that the lesions involved bilateral adnexa and there was a possibility of endometriosis decidualization, which was a benign disease, a conservative approach was recommended. However, if the disease was malignant, there were risks of tumor cells dissemination and tumor rupture. After a detailed preoperative informed consent, laparoscopic ovarian cystectomy and lesion resection was performed. Under the laparoscopy, the left ovarian multilocular cyst tightly adhered to the 3-month gravid uterus and mesorectum. Raising the uterus softly, the right ovarian cyst tightly adhered to the pelvic wall. The rectouterine pouch was completely obliterated. When removing the ovarian cysts and the lesion at the rectouterine pouch, papillary nodules inside the capsule were completely exposed and looked like malignancy ( Fig. 2 ). However, frozen-section revealed that both ovarian cysts and lesion at the rectouterine pouch were endometriosis, with decidualization of ectopic endometrial stroma. This result was confirmed by deferred pathology ( Fig. 2 ). Because of the large size of uterus, it was difficult to expose the rectouterine pouch completely. Some lesions remained residual in the pelvic. The patient recovered well after surgery. Then she was transferred to the department of obstetrics for high-risk pregnancy supervision. The baby, weighing 2500 g was delivered at 39 weeks by cesarean section because of FGR. During cesarean section, no obvious abnormality was found at bilateral adnexa and the uterus. The young woman prepared to come back for medication management after breast feeding. Fig. 2 Glandular structures with decidualized stroma were observed in the subepithelial layer of both ovary cysts and rectouterine pouch mass by laparoscopy and pathology examination ( × 40). Fig. 2 Glandular structures with decidualized stroma were observed in the subepithelial layer of both ovary cysts and rectouterine pouch mass by laparoscopy and pathology examination ( × 40).

Lingjie Bao: Writing – original draft, Project administration, Funding acquisition. Ting Wang: Supervision. Yinping Xiao: Data curation. Shouxin Gu: Data curation. Xiaoyu Zhou: Supervision. Yunxi Zheng: Supervision. Yun Chen: Validation. Xiaofang Yi: Writing – review & editing, Funding acquisition.

The case report complies with all ethics regulations. Institutional review board approval of OBGY hospital of Fudan University (2022-152).

Written informed consent from the patient for publication was obtained.

This project was supported by the 10.13039/501100009584 Clinical Research Foundation of Shanghai Municipal Health Commission( 20214Y0218 ), the Key Technologies Research and Development Program ( 2022YFC2704000 ) and 10.13039/501100016983 Shanghai Clinical Research Center for Gynecological Diseases( 22MC1940200 ).

No additional information is available for this paper.

Ovarian cancer in pregnancy is quite rare, with an incidence of 1 in 15,000 to 1 in 32,000 [ 1 ]. Once the adnexal mass in pregnancy was suspicious of malignancy, torsion or rupture, surgery should be considered. Treatment approach and operation time would be decided according to pathology of adnexal mass, the stage of the disease, gestational age and also desire of the patient. Endometriosis is a common disease that affects almost 10 % reproductive aged women [ 2 ]. It could be classified into ovarian endometrioma, superficial peritoneal lesions and deep endometriosis [ 2 ]. During pregnancy, the hormonal milieu specialized with the high progesterone levels may result in the increased glandular epithelial secretions, edema, and stromal vascularity of ectopic endometrium. This procedure is defined as decidualization, which may mimic malignancies on imaging and clinical evaluation [ 3 ]. Here we present a rare case whose decidualized bilateral ovarian endometriomas and rectouterine deep endometriosis clinically disguised as ovarian tumor with a metastasized lesion that occurred in the second trimester of pregnancy.

Pregnancy is a special physiological process with a changed hormonal milieu where benign pathologies would exhibit imaging appearances that may mimic malignancy [ 4 ]. Endometriosis decidualization is such a kind disease. During pregnancy, except for the eutopic endometrium, ectopic endometrium which originates from ovarian endometriomas and deep endometriosis implants would also undergo decidualization, which refers to increased glandular epithelial secretions, edema, and stromal vascularity. Decidualization could mimic malignancy and cause diagnostic dilemma on clinical evaluation and imaging [ 5 ]. Few publications demonstrated the clinical characteristic and the treatment of endometriosis decidualization during pregnancy. Some retrospective studies reported that 12–16 % pregnant women with endometriosis would experience endometriosis decidualization during pregnancy [ 6 , 7 ]. Most women diagnosed with ovarian endometriosis decidualization underwent oophorectomy or cystectomy in pregnancy as reported in literature [ 8 ]. However, a prospective observational cohort study reported that 50 % women with deep and/or ovarian endometriosis would experience decidualization of endometriotic cysts during pregnancy. In this cohort, 85 % women with endometrioma experienced cyst regression and 84 % women with nodules experienced nodule regression [ 9 ]. Another prospective observational cohort study reported that 54 % of women pre-diagnosed with endometriosis before conception experienced decidualization, which persisted throughout pregnancy and resolved by the time of final examination, 2–3 months after delivery [ 10 ]. Based on these observations, it is important to detect endometriotic lesions before pregnancy and reduce unnecessary surgical intervention. Treatment for endometriosis decidualization during pregnancy remains controversial. It is suggested that if the diagnostic accuracy could be improved, surgeries during pregnancy should be avoided or at least delayed until the term or postpartum period [ 11 ]. On the other hand, if surgery is decided, a conservative intervention, ovarian cystectomy rather than oophorectomy should be adopted since the lesion is most likely benign [ 12 ]. However, diagnosing endometriosis decidualization during pregnancy is quite difficult. When the disease involves unilateral adnexa, salpingo-oophorectomy would be performed if malignancy is suspected, in order to reduce the risk of tumor rupture and prevent dissemination of tumor cells [ 8 ]. In this case, treatment is difficult to determine. Firstly, all of the pelvic masses had never been detected before conception. Ovary cysts grew with abundant vascularization of intraluminal solid components. Secondly, the lesions that TVS and MRI suggested to be malignancy involved bilateral adnexa, and also the rectouterine pouch. Thirdly, these pelvic masses were of high risks of getting rupture. As reported that one decidualized ovarian endometrioma with size 7.0cm got rupture at the 36 weeks of gestation [ 13 ]. Decidualized rectovaginal deep endometriosis that occurred in the late third trimester of pregnancy was reported to cause spontaneous massive vaginal bleeding [ 14 ]. Considering these potential risks, MDT suggested to determine the pathology as soon as possible. Because this woman would continue the pregnancy if lesions were confirmed benign, ovary cystectomy was performed. Frozen section played a crucial role in surgical decision. Given that a long surgery could result in long term anesthesia, increase burden of cardiovascular system, cause heavy bleeding and also the risk of spontaneous abortion, we performed the operation within 2.5 hours, with some deep endometriosis lesion residual. Pharmacological management was advised after her breast feeding. Last but not least, endometriosis has been reported to correlate with adverse pregnancy outcome. A population-based, retrospective observational study enrolled 8,584,269 women with singleton and spontaneously conceived pregnancy [ 15 ]. It found that endometriosis was associated with significantly higher risk of maternal complications, including pre-eclampsia and eclampsia, antepartum hemorrhage, placenta previa, cesarean delivery, post-partum hemorrhage, disseminated intravascular coagulation (DIC), transfusion, hemoperitoneum, and prolonged hospitalization(>6 days). For fetal outcomes, endometriosis showed higher risk of intrauterine growth restriction (IUGR), premature birth, birth defects and abortion. For our case, the patient had cesarean section because of FGR at 39 weeks. The underlying mechanism of endometriosis-related adverse pregnancy outcome remains not fully understood. Progesterone resistance and inadequate uterine contractility may play a role in deferred implantation and misguided embryo placement, resulting in miscarriage, recurrent pregnancy loss and placenta previa. While, inflammation, activation of reactive oxygen species and the junctional zone alteration might promote the shallow trophoblast invasion, contributing to preeclampisa and preterm birth [ 16 ].

Here we report one case of synchronous decidualized ovarian and rectouterine deep infiltrating endometriosis which mimick malignancy in the second-trimester of pregnancy. Early diagnosis of endometriosis lesions before pregnancy is of great importance to help identify “malignancy” and reduce the potential risk of maternal and fetal complications. A multidisciplinary discussion is essential for decision-making. Conservative treatment is recommended during pregnancy when decidualization of endometriosis is considered.

The authors declare the following financial interests/personal relationships which may be considered as potential competing interests:Lingjie Bao reports financial support was provided by the 10.13039/501100009584 Clinical Research Foundation of 10.13039/100017950 Shanghai Municipal Health Commission . Xiaofang Yi reports financial support was provided by the 10.13039/501100012165 Key Technologies Research and Development Program . Xiaofang Yi reports financial support was provided by 10.13039/501100016983 Shanghai Clinical Research Center for Gynecological Diseases. If there are other authors, they declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Data and materials of this study were available from the first author upon reasonable request.