Pregnancy-related decidualization in post-cesarean section scar endometriosis: A case report

In July 2021 a 38-year-old woman, with a known case of hypothyroidism, was electively referred to the OB ward in Fasa hospital for a cesarean section. The reason for choosing cesarean section over vaginal delivery was prior cesarean section. The patient was G 6 P 2 at the time of admission, two of the gravidities being abortion and one of which being molar pregnancy. The intended offspring's gestational age was 38 weeks and 1 day. There was neither clinical nor paraclinical clue for endometriosis until the 16th week of pregnancy when a routine OB, NT/NB, uterus, and ovaries ultrasonography was performed for the patient. In this modality, the radiologist observed a 38 × 29 × 26 mm lobulated solid lesion within the rectus abdominis muscle located in the midline of the suprapubic abdominal wall. The radiologist's primary differential diagnosis for this lesion was scar endometriosis. During hospitalization, laboratory studies were performed. The patient showed normocytic anemia (MCV: 83.5, Hb:10.1) and mild hypokalemia (K: 3.3). Cesarean section was performed for the patient under spinal anesthesia; the abdominal wall was opened by a Pfannenstiel incision, and the lesion which was revealed by ultrasonography, was resected. Macroscopic evaluation of the lesion revealed fibrofatty tissue measuring 40 × 20 × 5 mm which displayed a homogenous whitish surface on the serial cut sections. No local hemorrhage was seen. Histological evaluation of the specimen showed endometrial glands surrounded by severely decidualized stroma. There was evidence of mild acute inflammation on top of chronic inflammation in the periglandular area being observed less commonly in the stroma. ( Fig. 1 and Fig. 2 ). Fig. 1 Endometrial glands with severe decidualized stroma. (H&E stain with ×40 magnification). Fig. 1 Fig. 2 Endometrial glands surrounded by decidualized stroma. (H&E stain with ×100 magnification). Fig. 2 Endometrial glands with severe decidualized stroma. (H&E stain with ×40 magnification). Endometrial glands surrounded by decidualized stroma. (H&E stain with ×100 magnification). In regards to the medical history of the patient, first of all, there was no evidence as to why the patient had undergone cesarean section in her previous pregnancies, what the causes of abortions were, or when the abortions and the molar pregnancy took place. Secondly, regarding hypothyroidism, the patient had been taking 100 μg of levothyroxine orally as a daily dose except for Fridays when she had been taking 200 μg of levothyroxine. Approximately 16 months after the delivery of the 6th gravidity, the patient was referred to a general surgeon, her chief complaint being abdominal pain at the site of the previous Pfannenstiel incision. Further examinations showed a retractable abdominal mass on the site of the Pfannenstiel incision without any sign of strangulation. The surgeon consequently performed open abdominal hernia (incisional hernia) repair with a mesh graft. A 3 × 3 cm defect on the left lower abdominal wall responsible for the incisional hernia was found. Fig. 3 summarizes the clinical course of the patient. Fig. 3 An overview of the clinical course of the case from the 6th gravidity until her recent hospitalization due to incisional hernia. Fig. 3 An overview of the clinical course of the case from the 6th gravidity until her recent hospitalization due to incisional hernia.

Amin Kavari [Writing - Original Draft, Review, and editing]. Babak Samizadeh [Conceptualization, Methodology, Data Curation, Project Administration and submission]. Maryam Maghbool [Conceptualization, Methodology, Data Curation, and Project Administration].

Written informed consent was obtained from the patient for publication and any accompanying images. A copy of the written consent is available for review by the Editor-in-Chief of this journal on request.

This study was conducted in full compliance with ethical standards and received approval from the Ethics Committee of Fasa University of Medical Sciences under the ethical code IR.FUMS.REC.1403.059.

The authors received no financial support for the research, authorship, and/or publication of this article.

Not applicable.

Maryam Maghbool.

Endometriosis is the presence of endometrial tissue outside of the endometrium and myometrium, consisting of endometrial glands and stroma [ 1 ]. The classic symptoms associated with this disease are dysmenorrhea and pelvic pain, menstrual irregularities, and infertility [ 12 ]. While the exact incidence varies across studies, recent literature suggests that scar endometriosis is a rare complication, occurring in approximately 0.03 % to 2 % of women who have undergone cesarean section [ 13 , 14 ]. Approximately 1.3 % of cases of endometriosis are located in the abdominal wall. Despite its rarity, cesarean section scar is, by far, the most common site for abdominal endometriosis (approximately 59 %) [ 15 ]. Our case report presented a 38-year-old G 6 P 2 woman in which subcutaneous endometriosis was ruled in by ultrasonography and was diagnosed by microscopy. The lesion's size had not grown since the radiologist had evaluated the lesion. Whether it was due to suboptimal healthcare or simply the absence of symptoms, physical examinations of our patient showed nothing problematic. The symptom could have been painless or painful, firm subcutaneous nodule. [ [4] , [5] , [6] , [7] , [8] , 10 , 11 ] Decidualization of endometriosis can happen under the influence of high progesterone levels. This progesterone can be supplied by either pregnancy or exogenous progesterone consumption. This process would induce atypia (nucleomegaly, prominent nuclei, peripheral margination of chromatin) among decidualized cells to some capacity [ 5 , 10 ]. There are but more differences between decidualized and non-decidualized endometrial tissues. There is evidence that stromal cells are the dominant component [ 8 ]. Qualitatively, non-decidualized endometriosis consists of stromal cells that retain their spindle shape and basophilic cytoplasm whereas decimalized endometriosis consists of polygonal stromal cells with abundant amphophilic cytoplasm [ 6 , 8 ]. To our knowledge, we present the ninth case report of decidualized endometriosis located on a post-cesarean section scar [ [4] , [5] , [6] , [7] , [8] , [9] , [10] , [11] ]. Pellegrini et al. [ 10 ] were the first to describe such endometriosis. The most important point he made was that pathologists and dermatologists might mistake decidualized endometriosis for malignancy. For instance, Myxoid change is a rare misleading finding in endometriosis that can be misinterpreted as malignancy [ 4 , 7 , 11 ]. Fortunately, there are some differentiative factors. Atypia and mitotic figures are not characteristics of endometriosis and are seen in malignancies [ 7 , 8 , 10 ]. Not seeing mitotic figures and atypia is in favor of endometriosis [ 7 ]. Contributing factors that may lead clinicians to the diagnosis of malignancy are extrapelvic localization of endometriosis, absence of glands in the tissue, and an elderly non-pregnant patient [ 4 , 10 ]. Immunophenotyping alongside microscopy can confirm the diagnosis of endometriosis. CD10 is diffusely present in endometrial stromal cells [ 4 , 5 ]. Knowing the fact that the presentation of CD10 is sensitive but non-specific [ 5 ], negative CD10 immunochemistry results can significantly improve the accuracy of our diagnosis. Regarding our case, the patient had not experienced endometriosis before. This lesion was located outside the pelvic cavity. On the other hand, the patient was in the younger demographics, and histopathologically, despite its scarcity, her resected tissue contained glandular structures favoring endometriosis over malignancy. There was no pathologic change in favor of malignancy in our case. Unfortunately, we didn't evaluate the expression of the CD10 marker, while it could help better differentiate the decidualized endometriosis from malignancy. Our case and similar previous cases [ [4] , [5] , [6] , [7] , [8] , [9] , [10] , [11] ] suggest that mechanical transportation of the endometrium from the uterus to the subcutaneous tissue of the abdominal wall is mostly involved in the pathogenesis [ 1 ]. In summary, we described a case of post-cesarean section endometriosis in which the presence of this endometriosis was first ruled in, in the second trimester. After delivery, microscopy from resected tissue showed endometrial glands surrounded by severely decidualized stroma. There was evidence of mild acute inflammation on top of chronic inflammation in the periglandular area being observed less commonly in stroma. While our case was in the younger demographics and histopathologically her resected tissue contained glandular structures, no past medical history of endometriosis, extrapelvic localization of the tissue could have led us to a diagnostic pitfall. Precisely differentiating cutaneous decidualized endometriosis from malignancies should be of great importance for dermatologists and pathologists.

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We searched for “(Endometriosis [tiab] OR endometriotic [tiab] OR endometrioma [tiab]) AND (deciduation [tiab] OR decidualization [tiab] OR decidua [tiab] OR decidualized [tiab]) AND (cesarean [tiab] OR caesarean [tiab] OR surgery [tiab] OR Skin [tiab] OR cutaneous [tiab] OR Pfannenstiel [tiab]) AND (case report)” in PubMed database. Relevant articles were obtained in full text. The bibliographic search ended on February 4th, 2024. The work has been reported in line with the SCARE criteria [ 16 ].

Endometriosis is defined as the presence of the functional layer of the endometrium outside the uterus [ 1 ]. 10 % of the women within the reproductive age would experience endometriosis [ 2 ]. Endometriosis is frequently located in organs adjacent to the uterus namely the cervix, vagina, vulva, rectovaginal septum, ovary, fallopian tubes, uterine ligaments, appendix, small and large bowel, bladder and ureters, pelvic peritoneum, etc [ 1 ] However, the location of endometriosis is not confined to adjacent sites, extending to remote areas such as the lung, pleura, peripheral nerves, and skin. Despite its rarity, post-cesarean section endometriosis is a common occurrence among endometriosis caused by surgical scars [ 1 , 3 ]. It is believed that this disease is caused by the iatrogenic deposition of tissue in the surgical scar [ 3 ]. As endometriosis is subordinate to hormonal changes, it can potentially mimic the changes in the endometrium via conception or exogenic estrogen consumption. There are several case reports describing decidualization in post-cesarean section endometriosis [ [4] , [5] , [6] , [7] , [8] , [9] , [10] , [11] ]. In these prior reports, the issue was that this condition may be misinterpreted as malignancy due to its location and atypia of the cells [ 4 , 6 ]. Herein, we report the 9th case of pregnancy-related decidualization in post-cesarean section scar endometriosis [ [4] , [5] , [6] , [7] , [8] , [9] , [10] , [11] ]. To the best of our knowledge, few cases of pregnancy-related decidualization in post-cesarean section endometriosis have been reported so far. There is a lack of evidence regarding this phenomenon. We thereupon present the 9th case of pregnancy-related decidualization in post-cesarean section endometriosis.

None.