Scar endometriosis as an easily misdiagnosed abdominal mass: a case report and review of the literature

Endometriosis is characterized by the presence of ectopic endome- trial-like glands and stroma outside the uterus [1]. This common disease affects 5% to 10% of all menstruating women and primarily affects pelvic sites such as the ovaries, uterine ligaments, and peri- toneum [2,3]. Extrapelvic endometriosis can occur in atypical loca- tions, ranging from the gastrointestinal tract to the central nervous system [4,5]. Scar endometriosis, a form of extrapelvic endometrio- sis, is marked by a tender nodule that worsens progressively in sync with the menstrual cycle, reflecting its estrogen dependence. It is often misdiagnosed due to its rarity and variable presentation, al- though diagnostic imaging can help rule out other conditions [6,7]. This study examined a case of scar endometriosis that was inciden- tally identified on a computed tomography (CT) scan without any symptoms and reviewed the literature to facilitate early diagnosis and prompt treatment based on the patient’s medical history and physical examination. Chi Hyun Lee1, Changryul Claud Yi1,2, Ji Hyun Ahn2,3, Joo Hyoung Kim1,2,* 1Department of Plastic and Reconstructive Surgery, Pusan National University School of Medicine, Busan, Korea 2Biomedical Research Institute, Pusan National University Hospital, Busan, Korea 3Department of Pathology, Pusan National University Hospital, Busan, Korea Scar endometriosis, which is characterized by ectopic endometrial-like glands and stro- ma surrounding scar tissue, is rare and presents diagnostic challenges due to its incon- sistent presentation. We report a case of a 40-year-old woman who had previously un- dergone two cesarean sections and a hysterectomy, in whom a mass in the subcutane- ous layer of the lower abdomen was incidentally discovered by computed tomography (CT). A physical examination revealed a linear cesarean scar with a palpable, pigmented mass. An enhanced abdominal CT scan revealed an approximately 3.5-cm ill-defined soft tissue mass infiltrating the rectus abdominis muscle. A desmoid tumor was sus- pected based on the radiological findings, and endometriosis was also considered in light of the patient’s medical history. Wide mass excision was performed, ensuring 5-mm margins. The mass was completely excised, and a histopathological examination revealed endometriosis. Due to its rarity, scar endometriosis in the abdominal area can be easily misdiagnosed. Therefore, a heightened suspicion of scar endometriosis should be maintained in female patients with a history of abdominal or pelvic surgery presenting with an abdominal mass. Although imaging modalities can play a support- ive role in the diagnosis, an extensive medical history assessment and comprehensive physical examination remain crucial.

Cicatrix / Endometriosis / Hysterectomy / Neoplasms / Case reports This work was supported by a clinical research grant from Pusan National University Hospi- tal in 2022. Received: Feb 16, 2024 Revised: Apr 22, 2024 Accepted: Apr 23, 2024 Correspondence: Joo Hyoung Kim Department of Plastic and Reconstructive Surgery, Pusan National University Hospital, Pusan National University School of Medicine, 179 Gudeok-ro, Seo- gu, Busan 49241, Korea. E-mail: [email protected] *Current affiliation: Department of Plastic and Reconstructive Surgery, Good Moonhwa Hospital, Busan, Korea Copyright © 2024 The Korean Society for Aesthetic Plastic Surgery. This is an Open Access article distributed under the terms of the Creative Commons At- tribution Non-Commercial License (https://creativecommons.org/licenses/by-nc/4.0/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited. www.e-aaps.org https://doi.org/10.14730/aaps.2024.01109 Arch Aesthetic Plast Surg 2024;30(2):82-85 pISSN: 2234-0831 eISSN: 2288-9337 83 aaps Archives of Aesthetic Plastic SurgeryLee CH et al. Scar endometriosis: easily misdiagnosed mass CASE REPORT A 40-year-old woman presented with a soft tissue mass in the low- er abdomen, which was incidentally discovered on CT imaging in 2023 for the evaluation of primary aldosteronism. The patient’s surgical history included two uncomplicated cesarean sections be- tween 2014 and 2015, a hysterectomy for dysmenorrhea, and the removal of a right ovarian cyst in 2017. She noticed a palpable lump a month previously but reported no abdominal discomfort or cyclical symptoms. Physical examination revealed a linear cesarean scar accompa- nied by a centrally located, mildly palpable, indistinct mass with pigmentation (Fig. 1). Further CT imaging showed an ill-defined soft tissue mass, approximately 3.5 cm along its long axis, infiltrat- ing the rectus abdominis muscle (Fig. 2). Based on these radiologi- Fig. 1. Linear cesarean scar , accompanied by a centrally positioned, mildly palpable, and indistinct mass exhibiting pigmentation. Fig. 2. Ill-defined soft tissue density lesion in the subcutaneous layer of the lower abdomen. Fig. 3. A round mass with unclear borders. Fig. 4. Histological findings. (A, B) A hematoxylin and eosin-stained section from an abdominal mass biopsy showed cystically dilated endome- trial-type glands and stroma (A: × 40, B: × 200). (C, D) Immunohistochemical studies ( × 200). The stroma cells were positive for CD10 and neg- ative (cytoplasmic positive) for beta-catenin. A C B D 84 aaps Archives of Aesthetic Plastic Surgery VOLUME 30. NUMBER 2. APRIL 2024 cal findings, a desmoid tumor was suspected. Considering the pos- sibility of endometriosis, as indicated by the patient’s medical his- tory, surgical removal with a 5-mm margin was performed. During the surgery, the fibrotic scar was found to be strongly ad- herent to the fascia. The mass, along with the scar tissue, was com- pletely excised and appeared grossly as a rounded entity with indis- tinct borders (Fig. 3). Histopathological examination showed cysti- cally dilated endometrial-type glands and stroma, confirming the presence of endometriosis. Additionally, immunohistochemical analysis indicated that the stromal cells tested positive for CD10 and negative (with cytoplasmic positivity) for beta-catenin (Fig. 4). Fol- lowing the surgery, the patient was referred for hormone therapy, and treatment with a gonadotropin-releasing hormone agonist was initiated. The patient recovered well and experienced no recurrence of the condition (Fig. 5).

Scar endometriosis is a rare condition that primarily affects young women of reproductive age and is frequently misdiagnosed due to its low incidence (0.07%–0.47%). This condition usually appears after abdominal or pelvic surgery, especially following early hyster- otomy and cesarean section [8,9]. The iatrogenic direct implanta- tion theory provides the best explanation for this relationship, sug- gesting that the inadvertent introduction and implantation of en- dometrial tissue into surgical wounds during procedures can lead to the development of scar endometriosis [10]. The symptoms of scar endometriosis commonly include cyclic pain associated with menses, dyspareunia, and dysmenorrhea. How- ever, the onset of symptoms can vary widely, occurring months to years after the initial surgery, and some studies have reported that only 20% of patients exhibit symptoms [2,11]. Additionally, the le- sions can display a wide range of colors, depending on the depth and extent of the associated hemorrhage. Due to these varied presenta- Fig. 5. A postoperative photograph taken 1 year after surgery. tions, diagnosing this condition is challenging, with one study report- ing an accuracy rate of less than 50% for the initial diagnosis [8,12]. Diagnostic imaging findings can be helpful but are typically non- specific. Therefore, it is essential to consider a broad spectrum of other diseases that may manifest as a mass in the abdominal wall, including sarcoma, desmoid tumor, lymphoma, hypertrophic scar, and hernia [13,14]. CT and magnetic resonance imaging are also crucial in the preoperative assessment of the extent of the disease. Ultimately, the diagnosis is confirmed histopathologically by the presence of endometrial glands and stroma [15]. The optimal treatment for scar endometriosis involves wide local excision, ensuring a sufficient margin of 5–10 mm of healthy tissue around the mass, with special attention to preventing subsequent re- implantation. Additionally, because the lesion is sometimes densely adherent and extensively involves the abdominal rectus fascia, prox- imity to a synthetic graft may be necessary [13]. Furthermore, al- though rare, careful observation is necessary due to the potential for scar endometriosis to transform into clear cell carcinoma. The effi- cacy of hormone therapy as a standalone treatment is limited, and hormone therapy is more commonly used as an adjunct to surgical excision, primarily to decrease lesion size preoperatively [7]. In conclusion, surgeons should maintain a high index of suspi- cion for scar endometriosis in young female patients presenting with abdominal masses who have a history of abdominal or pelvic surgery, regardless of their symptoms. Although imaging modali- ties can be useful, the patient’s medical history and physical exami- nation remain crucial. NOTES Conflict of interest No potential conflict of interest relevant to this article was report- ed. Ethical approval This report was approved by the Institutional Review Board of Pu- san National University Hospital (IRB No. 2307-027-129). Patient consent The patient provided written informed consent for the publication and the use of her images. ORCID Chi Hyun Lee https://orcid.org/0009-0006-5870-2664 Changryul Claud Yi https://orcid.org/0000-0002-4633-0043 Ji Hyun Ahn https://orcid.org/0000-0002-3312-788X Joo Hyoung Kim https://orcid.org/0000-0002-4893-3761 85 aaps Archives of Aesthetic Plastic SurgeryLee CH et al. Scar endometriosis: easily misdiagnosed mass

1. Chapron C, Marcellin L, Borghese B, et al. Rethinking mechanisms, di- agnosis and management of endometriosis. Nat Rev Endocrinol 2019; 15:666-82. 2. Marsden NJ, Wilson-Jones N. Scar endometriosis: a rare skin lesion presenting to the plastic surgeon. J Plast Reconstr Aesthet Surg 2013; 66:e111-3. 3. Taylor HS, Kotlyar AM, Flores V A. Endometriosis is a chronic sys- temic disease: clinical challenges and novel innovations. Lancet 2021; 397:839-52. 4. Min K, Han HH. Treatment of abdominal wall endometriosis using a mini-abdominoplasty design. Arch Aesthetic Plast Surg 2018;24:134-7. 5. Davis AC, Goldberg JM. Extrapelvic endometriosis. Semin Reprod Med 2017;35:98-101. 6. Hensen JH, Van Breda Vriesman AC, Puylaert JB. Abdominal wall endometriosis: clinical presentation and imaging features with em- phasis on sonography. AJR Am J Roentgenol 2006;186:616-20. 7. Vercellini P , Vigano P , Somigliana E, et al. Endometriosis: pathogene- sis and treatment. Nat Rev Endocrinol 2014;10:261-75. 8. Bektas H, Bilsel Y , Sari YS, et al. Abdominal wall endometrioma; a 10- year experience and brief review of the literature. J Surg Res 2010;164: e77-81. 9. Samal AG, Behera PK, Sahoo P . Abdominal scar endometriosis. Indian J Surg 2013;75(Suppl 1):217-9. 10. Eskenazi B, Warner ML. Epidemiology of endometriosis. Obstet Gy- necol Clin North Am 1997;24:235-58. 11. Col C, Yilmaz EE. Cesarean scar endometrioma: case series. World J Clin Cases 2014;2:133-6. 12. Din AH, Verjee LS, Griffiths MA. Cutaneous endometriosis: a plastic surgery perspective. J Plast Reconstr Aesthet Surg 2013;66:129-30. 13. Wolf GC, Singh KB. Cesarean scar endometriosis: a review. Obstet Gynecol Surv 1989;44:89-95. 14. Majors J, Stoikes NF , Nejati R, et al. Resection and abdominal wall re- construction of a desmoid tumor with endometrioma features. Case Rep Surg 2016;2016:9453450. 15. Danielpour PJ, Layke JC, Durie N, et al. Scar endometriosis: a rare cause for a painful scar: a case report and review of the literature. Can J Plast Surg 2010;18:19-20.