{"paper_id":"3d980f1d-5efc-42a7-9517-94f77c364e01","body_text":"Amsterdam UMC\nInguinal endometriosis, a rare entity of which surgeons should be aware: clinical\naspects and long-term follow-up of nine cases\nWolfhagen, N.; Simons, N. E.; de Jong, K. H.; van Kesteren, P. J. M.; Simons, M. P.\nPublished in:\nHernia\nDOI:\n10.1007/s10029-018-1797-x\nPublished: 01/01/2018\nDocument Version\nPublisher's PDF, also known as Version of record\nDocument license\nTaverne\nLink to publication\nCitation for pulished version (APA):\nWolfhagen, N., Simons, N. E., de Jong, K. H., van Kesteren, P. J. M., & Simons, M. P. (2018). Inguinal\nendometriosis, a rare entity of which surgeons should be aware: clinical aspects and long-term follow-up of nine\ncases. Hernia, 22(5), 881-886. https://doi.org/10.1007/s10029-018-1797-x\nGeneral rights\nIt is not permitted to download or to forward/distribute the text or part of it without the consent of the author(s) and/or copyright holder(s),\nother than for strictly personal, individual use, unless the work is under an open content license (like Creative Commons).\nDisclaimer/Complaints regulations\nIf you believe that digital publication of certain material infringes any of your rights or (privacy) interests, please let the Amsterdam UMC\nMedical Library know, stating your reasons. In case of a legitimate complaint, the Medical Library will make the material inaccessible and/or\nremove it from the website. Contact address: outputregistratie@amsterdamumc.nl\nDownload date: 02. Aug. 2026\n\nVol.:(0123456789)1 3\nHernia (2018) 22:881–886 \nhttps://doi.org/10.1007/s10029-018-1797-x\nORIGINAL ARTICLE\nInguinal endometriosis, a rare entity of which surgeons should be \naware: clinical aspects and long-term follow-up of nine cases\nN. Wolfhagen1 · N. E. Simons2 · K. H. de Jong3 · P . J. M. van Kesteren4 · M. P . Simons5\nReceived: 14 April 2018 / Accepted: 13 July 2018 / Published online: 4 August 2018 \n© Springer-Verlag France SAS, part of Springer Nature 2018\nAbstract\nIntroduction Inguinal endometriosis is a rare disease and often misdiagnosed for other, more common groin pathology. We \npresent nine cases of women with inguinal endometriosis with long-term follow-up.\nMethods In this retrospective case series, the Dutch PALGA system was searched for all patients diagnosed with extrapel-\nvic endometriosis located in the groin in the OLVG hospital, Amsterdam, between 2000 and 2016. Relevant information \nregarding pre- and postoperative characteristics and symptoms was collected. Follow-up consisted of a telephone call from \nthe attending surgeon.\nResults None of the patients had a history of pelvic endometriosis. Typically, they presented with a right-sided swelling in the \ngroin. Preoperative ultrasound and MRI were in most cases inconclusive. In one of two patients fna indicated endometriosis. \nIn only three patients the surgeon considered the diagnosis endometriosis preoperatively. Surgical removal was effective \nwith no reported complications. A coexisting hernia sac was resected in four cases, and there was a suspicion of a persistent \nprocessus vaginalis (canal of Nuck) in three, suggesting that a persistent processus vaginalis is possibly an important key to \nthe pathogenesis. In none of the cases there was an indication for mesh implantation. One patient was later diagnosed with \npelvic endometriosis.\nConclusion Follow-up by a gynecologist is advised to check for intra-abdominal disease and inform patients on fertility \nperspective. Surgeons should be aware of the possibility of inguinal endometriosis in fertile women with a lump in the groin.\nKeywords Inguinal hernia · Endometriosis · Groin · Processus vaginalis\nIntroduction\nEndometriosis is defined as the presence of endometrial \ngland cells and stroma outside the uterine cavity. Endo-\nmetriosis is a common benign inflammatory disease with \na reported prevalence of 1.2–1.5%, with a peak prevalence \nbetween the age of 35 and 44, usually situated within the \npelvis [1]. Extrapelvic endometriosis is less common, but \ncan involve nearly all organs [2].\nInguinal endometriosis is rare with a reported incidence \nof < 1% of patients with endometriosis [3 –6]. It is defined \nas endometriosis in the inguinal canal, either in a hernia sac, \nsurrounding the round ligament or in a persistent processus \nvaginalis (PPV). A PPV, a small invagination of the parietal \nperitoneum, is also known as the persistent canal of Nuck. \nDue to its location in the groin, symptomatic patients are \noften presented to a general surgeon rather than a gynecolo-\ngist. Because of its rare and uncommon presentation, endo-\nmetriosis of the groin is frequently clinically misdiagnosed \nas a lymph node, cyst of Nuck, femoral or inguinal hernia \nor a lipoma [7–9]. Inguinal endometriosis is prone to diag-\nnostic uncertainty, which possibly leads to multiple and \nexpensive preoperative imaging. The disease itself remains \nenigmatic because inguinal endometriosis grows outside the \npelvic peritoneal cavity and, intriguingly, preferably in the \n * M. P. Simons \n m.p.simons@olvg.nl\n1 Department of Surgery, Flevoziekenhuis, Almere, \nThe Netherlands\n2 Department of Obstetrics and Gynecology, Academic \nMedical Center, Amsterdam, The Netherlands\n3 Department of Surgery, Academic Medical Center, \nAmsterdam, The Netherlands\n4 Department of Obstetrics and Gynecology, OLVG, \nAmsterdam, The Netherlands\n5 Department of Surgery, OLVG, Oosterpark 9, \n1091 AC Amsterdam, The Netherlands\n\n882 Hernia (2018) 22:881–886\n1 3\nright inguinal canal. Several theories have been proposed, \nincluding but not limited to metaplasia of mesothelium, ret-\nrograde menstruation and seeding into a hernia or PPV, oxi-\ndative stress and inflammation, auto-immune dysfunction, \napoptosis suppression and regeneration of stem cells [10]. \nHowever, none of them fully elucidate its pathogenesis [4 , \n6, 11, 12].\nOnly a limited number of cases have been reported in \ncontemporary literature. We present clinical aspects of nine \nindividual cases of inguinal endometriosis with their long-\nterm follow-up, and considerations on its diagnosis, treat-\nment and pathogenesis are discussed.\nMethods\nWe searched the Dutch PALGA system, a nationwide histo-\npathology and cytopathology data network and archive, for \npatients who were diagnosed with extrapelvic endometrio-\nsis located in the groin in the OLVG hospital, Amsterdam, \nbetween 2000 and 2016 [13]. Furthermore, we identified all \nfemale patients treated for an inguinal hernia in the same \ntime period to estimate the incidence of the inguinal endo-\nmetriosis in this patient group at our hospital.\nFor all patients that had received surgical treatment for \nendometriosis in the groin, the following data were col-\nlected: age, relevant medical history, initial symptoms, \nlocation of the swelling, preoperative imaging, preopera-\ntive fine needle aspiration (fna) and pathology results, type \nof primary surgery, pathology results of the resected tissue \nand results of short-term follow-up. After current inclusion, \npatients received follow-up from the attending surgeon by a \nsemi-structured telephone call. If required or requested by \nthe patient they also received evaluation by a gynecologist .\nResults\nA total of nine women were included. In the same period in \nour hospital, 592 female patients were operated for a hernia \nor swelling in the groin giving an estimated incidence of \n9/592 (1.5%). The mean age of women included in this study \nwas 32.5 years (range 27–43 years) at the time of operation. \nAll patients presented with a swelling in the groin (Table 1). \nThree patients presented with complaints of cyclical pain \nsolely in the groin and one with cyclical pain in the lower \nabdomen radiating to the groin. Physical examination \nrevealed a swelling in the right groin in seven patients, and \nin two on the left side. Time of complaints prior to surgery \nvaried from 1 month up to 2 years. None of the patients had \na history of pelvic endometriosis.\nIn seven patients an ultrasound (US) of the groin was \nperformed. In only one patient this was suggestive for \nendometriosis. In four patients an MRI was performed \nadditionally to the US. None of the MRI’s offered the (dif-\nferential) diagnosis of endometriosis. Preoperative imaging \nwas suggestive for an inguinal hernia in three patients. Pre-\noperative diagnostic fna was performed in two patients. In \none patient the cytology report showed endometriosis, for \none patient fna was inconclusive.\nPeroperatively, an endometrial cyst was suspected in five \npatients. Four patients had an inguinal hernia. Three patients \ndid not have an inguinal hernia with a hernia sac; however, a \nPPV was described or suspected. In two patients, there was \nno documentation of the operation and, therefore, no details \nof per-operative findings are known.\nFollowing the diagnosis endometriosis of the groin, only \nthree of nine women were seen by a gynecologist for evalu-\nation. One woman had complaints of dysmenorrhea and \nsuperficial dyspareunia. Diagnostic laparoscopy confirmed \npelvic endometriosis according to the American Fertility \nSociety classification (AFS) I–II. Others had no (known) \nhistory of endometriosis and no pelvic endometriosis was \nfound. Five women were nulliparous, in two parity was \nunknown. At short-term follow-up, the remaining patients \nhad no complaints related to the operation or a possible \nrecurrence of disease.\nTelephone follow-up was attempted in all patients. \nThree women were lost to follow-up due to change of con-\ntact details and unknown current address. Follow-up of \nsix patients, with an average of 6 years (range 2–9 year), \nrevealed that none had recurrence of disease (i.e. inguinal \nendometriosis). Five patients had complaints of dysmenor -\nrhea, possibly related to endometriosis. These patients had \nnot consulted a physician with these complaints. Nonethe-\nless, only one of these patients received follow-up and treat-\nment for endometriosis and subfertility by a gynecologist. \nAll patients contacted by telephone would appreciate follow-\nup by a gynecologist.\nDiscussion\nIn this case series, we report nine women treated for an \ninguinal swelling containing inguinal endometriosis, of \nwhich six were successfully contacted for long-term follow-\nup. Our case series gives insight into relevant preoperative \nand postoperative aspects.\nSwelling in the right side of the female groin, in particular \na painful swelling with cyclic symptoms related to menstrua-\ntion, must guide the diagnosis towards inguinal endometrio-\nsis. However, in many cases symptoms are not recognized as \nsuch, resulting in incorrect clinical preoperative diagnosis \nof other, more common, groin pathology such as inguinal \nor femoral hernia, lymph nodes, a cyst of Nuck or swellings \narising from structures in the skin such as cysts and lipomas \n\n883Hernia (2018) 22:881–886 \n1 3\n[8]. Three out of nine cases were diagnosed preoperatively, \nwhich is consistent with reported numbers in literature of \nless than 50% [ 11]. This might be due to the uncommon \nlocation of the endometriosis, the non-cyclic pain pattern in \na number of patients [4, 14, 15] or inconclusive results from \nimaging [5, 7, 8, 16–18].\nIn case of a swelling in the groin of unknown etiology, \npreoperative imaging might be helpful to identify underly -\ning pathology. Nonetheless, surgery is often inevitable. In \nour series non-invasive imaging (ultrasound and MRI) had a \nvery low sensitivity. The exact sensitivity of a MRI in ingui-\nnal endometriosis is unknown. Ultrasound can be helpful \nto roughly differentiate between inguinal hernia, enlarged \nlymph nodes and cyst/masses, but further classification of \nlesions is complex [19]. Although MRI is a helpful diag-\nnostic tool for pelvic endometriosis (sensitivity of 90% and \nspecificity of 98%) [6 , 12], for extrapelvic endometriosis \nfamiliarity with the disease might be a more important factor \nfor the correct diagnosis [19]. It is argued that once there is \na suspicion for inguinal endometriosis, fna is an appropri-\nate diagnostic test [12, 14]. Fna was conclusive in one out \nof two patients, a comparable result with previous studies \nin inguinal-, abdominal- or scar endometriosis [20, 21]. We \ndo believe that when inguinal endometriosis is included in \nthe differential diagnosis, an ultrasound is first choice for \ndiagnostic purpose. If this is inconclusive and an inguinal \nhernia is excluded, fna could be a cost-effective workup to \nascertain the diagnosis and rule out other significant disease. \nTable 1  Clinical characteristics of nine patients with inguinal endometriosis\nCharacteristics pre- and postoperative and current status at follow-up\nUS ultrasound, PA pathological anatomy, fna fine needle aspiration\nPatient age \nat diagnosis \nparity\nYear of surgery pri-\nmary/secondary side of \nthe body\nComplaints Physical examination Preoperative diagnosis Follow-up\n28 years\nUnknown\n2011\nPrimary\nRight side\nSwelling and pain in \nthe groin\nReducible inguinal \nswelling\nUS + MRI: hypointens \nanomaly, no inguinal \nhernia\nSeen by doctor: com-\nplaints of back pain \nwith unknown etiology, \nno endometriosis found\nCyclical pain around scar\n36 years\nNulliparous\n2010\nPrimary\nLeft side\nSwelling in groin and \ncyclical abdominal \npain, radiating to the \ngroin\nReducible inguinal \nswelling 1–2 cm, \nvalsalva+\nUS: hernia inguinalis \nor endometriosis\nLost to follow-up\n43 years\nUnknown\n2013\nPrimary\nRight side\nSwelling in the groin Swelling in groin US + MRI: leiomyoma Not seen by doctor\nNumb feeling around \nscar\nIrregular menstrual cycle\n27 years\nNulliparous\n2015\nPrimary\nRight side\nSwelling in the groin Swelling in groin US: atypical lymph \nnode or sebaceous \ncyst\nfna: endometriosis\nNot seen by doctor\nNo complaints\n30 years\nNulliparous\n2008\nPrimary\nRight side\nSwelling and cyclical \npain in the groin\nSwelling in groin Not mentioned Lost to follow-up\n32 years\nNulliparous\n2010\nRecurrent hernia\nLeft side\nSwelling groin and \ncyclical abdominal \npain\nSwelling in groin US + MRI: bursitis, \ncyst of Nuck, bursa or \nlymph node\nSeen by doctor: exten-\nsive follow-up with \ngynecologist\nEndometrioses grade \n1–2, fertility problems\n29 years\nVaginal birth\nC-section\n2010\nPrimary\nRigth side\nSwelling in the groin Reducible inguinal/\nmedial swelling, \nvalsalva +\nUS: inguinal or medial \nhernia\nLost to follow-up\n36 years\nUnknown\n2008\nPrimary\nRight side\nSwelling in the groin Swelling in groin US: cyst of Nuck Not seen by doctor\nLess complaints since \ngestation\n32 years\nUnknown\n2008\nPrimary\nRight side\nSwelling and cyclical \npain in the groin\nSwelling in groin US + MRI: presumably \nincarcerated seba-\nceous cyst in hernia \ninguinalis\nfna: inconclusive\nNot seen by doctor\nMild complaints, irregu-\nlar cycle since 1 year\n\n884 Hernia (2018) 22:881–886\n1 3\nAlthough an MRI could be considered indicated to identify \ngroin pathology, in our series we do not deem an additional \nMRI of additive value to diagnose inguinal endometriosis.\nThe exact etiology of endometriosis is not clear. Although \nretrograde menstruation can explain how endometrial gland \ncells are found outside the uterine cavity, this does not com-\npletely explain why or how endometrium ends up in the \ngroin and in other organs that are not in contact with the \nabdominal cavity. Two theories of embryological origin \nhave been described, but none is proven. The first concerns \nthe metaplasia of coelomic mesothelial cells and the second \nseeding via an open route (Hernia or PPV) into the groin. \nBoth theories require a short explanation of the embryologi-\ncal development of the groin, which is complex.\nEpithelial cells of the uterus (endometrium) and the Fal-\nlopian tubes are formed in the embryo after differentiation \nof the epithelial cells of the Müllerian tube. These tubes \nare formed by invagination of mesothelial cells, forming \nthe parietal peritoneum and covering the urogenital ridges. \nDuring the fetal period, the peritoneal cavity will extend \nin the inguinal canal along the gubernaculum, forming the \nround ligament and creating the processus vaginalis. The \nprocessus vaginalis runs from the abdominal cavity to the \nlabium majus. Normally the processus vaginalis obliterates \nin the first year of life [6]. In both men and women there is a \nchance that this does not happen, leaving a PPV or remnants \nof the early peritoneal cells in the inguinal canal. These cells \nhave the same embryological source as the endometrium \ncells covering the lumen of the uterus and, therefore, the \ncells of the (microscopic) processus vaginalis can give rise \nto endometrial cells by metaplasia.\nThe second theory of inguinal endometriosis is based on \nthe presence of the PPV [6 , 12, 22], creating a pathway for \nendometrial cells to seed through this canal. A PPV can be \ndifficult to identify during surgery. It can be a very small \ndefect, with a lumen only identifiable by microscope. A \ncoexisting hernia sac has been found in several other stud-\nies [5, 6, 23], and also in our series we found a hernia sac in \nthree patients. In addition, in four others there was a fibrotic \nextension to the internal ring or a continuation of the struc-\nture into the abdominal cavity (following the round liga -\nment). These are all suggestive for a PPV. Both theories are \nrarely mentioned in previous reviews describing inguinal \nendometriosis [6, 12], but have been described in the etiol-\nogy of mesothelial cyst adjacent to the round ligament [9 , \n24–26].\nOur series shows that in most cases (seven out of nine \npatients) the swelling is on the right side. This is in line \nwith earlier reviews [3, 5, 6, 27]. The exact etiology for the \nright-sided preference is unknown but it is argued that the \nsigmoid has a preventive role in seeding on the left ingui-\nnal side [3 , 4, 18, 28]. Alternatively, it is hypothesized \nthat as the right processus vaginalis in men obliterates \nlater in childhood, this might be the same with the right \nprocessus vaginalis in women; however, this has not been \nproven. Furthermore, some studies plead for an asymmet-\nrical right-sided lymphatic drainage [4 , 5], explaining the \nfavorable side of endometriosis in the right inguinal canal, \nbut this has not been proven either.\nPrimary treatment of inguinal endometriosis relies \non complete surgical excision of the lesion to avoid sub-\nsequent recurrence [29]. In all patients in our series, \nopen excision was performed and sufficient, as none of \nthe patients had complaints of the groin after surgery at \nshort-term and long-term follow-up. Although reports \nhave shown that for some sites of inguinal endometriosis \na laparoscopic excision is advisable, this should only be \nrecommended in cases where an inguinal indirect hernia \nis present, making it possible to pull the lesion out of the \ninguinal canal. Mesh implantation might be indicated in \ncase of large defects after surgical resection of the endo-\nmetriosis and hernia sac; however, this was not consid-\nered necessary in our cases. Per-operative inspection of the \nlesion remains most important, as complete excision has a \npreventive role in the recurrence of endometriosis. Also, in \ncases where the etiology is unknown there is a very small \nrisk of a malignancy [30].\nSecondary to excision, we recommend follow-up by a \ngynecologist. Inguinal endometriosis has been shown to \nbe associated with pelvic endometriosis, although num -\nbers differ between various studies [ 3, 5, 6]. In our series, \nonly one patient had mild endometriosis at laparoscopy, \nand others had no (known) history of endometriosis and \nnegative results at physical examination. Intriguingly, five \nwomen were nulliparous, and two coped with subfertility, \nwith several fertility treatments. Subfertility has been men-\ntioned in most studies on inguinal endometriosis [4 , 23], \nso women should be examined for pelvic endometriosis \nand be informed on future fertility perspectives.\nThere are some limitations in this study. Due to its ret-\nrospective design, preoperative diagnostics were not stand-\nardized which is of importance considering the interpreta-\ntion of the reported pain in our patients. The existence of \npreoperative symptoms, in particular cyclical pain, could \nbe omitted in the charts for various reasons, such as insuf-\nficient anamnesis or documentation, but also because of \nthe absence of (cyclic) pain; it is a remarkable but well-\ndocumented phenomenon that in patients with endome-\ntriosis symptoms are poorly related to the stage of the \ndisease [31], and pain even can be absent. In addition, two \noperative charts were missing and follow-up could only be \ncompleted in six out of nine patients. Furthermore, due to \nthe rarity very little is investigated thoroughly.\n\n885Hernia (2018) 22:881–886 \n1 3\nConclusion\nThe presence of endometriosis should be considered in fer -\ntile women with a painful swelling in the groin. Surgeons \nshould be aware of this rare diagnosis and pay attention \nto gynecological complaints. Gynecological evaluation \nshould have an important role in the pre- and postopera-\ntive diagnosis.\nCompliance with ethical standards \nConflict of interest NW declares no conflict of interest. NS declares no \nconflict of interest. KDJ declares no conflict of interest. PVK declares \nno conflict of interest. MS declares no conflict of interest.\nEthical approval This article did not require ethical approval according \nto Dutch Law.\nHuman and animal rights  Human and/or animal rights were not vio-\nlated.\nInformed consent Patients were contacted by phone by the surgical \nteam that had performed the operation. If contacted and included, \ninformed consent was given by the participants during the phone call.\nReferences\n 1. Ballard KD, Seaman HE, De Vries CS, Wright JT (2008) Can \nsymptomatology help in the diagnosis of endometriosis? Find-\nings from a national case-control study—part 1. BJOG An Int \nJ Obstet Gynaecol 115(11):1382–1391. https ://doi.org/10.111\n1/j.1471-0528.2008.01878 .x\n 2. Machairiotis N, Stylianaki A, Dryllis G et al (2013) Extrapelvic \nendometriosis: a rare entity or an under diagnosed condition? \nDiagn Pathol 8:194. https ://doi.org/10.1186/1746-1596-8-194\n 3. Sun ZJ, Zhu L, Lang JH (2010) A rare extrapelvic endometrio-\nsis: inguinal endometriosis. J Reprod Med 55(1–2):62–66\n 4. Candiani GB, Vercellini P, Fedele L, Vendola N, Carinelli S, \nScaglione V (1991) Inguinal endometriosis: pathogenetic and \nclinical implications. Obstet Gynecol 78(2):191–194\n 5. Mourra N, Cortez A, Bennis M et al (2015) The groin: an unu-\nsual location of endometriosis—a multi-institutional clinico-\npathological study. J Clin Pathol 68(7):579–581. https ://doi.\norg/10.1136/jclin  path-2014-20281 2\n 6. Gaeta M, Minutoli F, Mileto A et al (2010) Nuck canal endo -\nmetriosis: MR imaging findings and clinical features. Abdom \nImaging 35(6):737–741. https ://doi.org/10.1007/s0026  \n1-010-9607-7\n 7. Albutt K, Glass C, Odom S (2014) Gupta a. Endometrio -\nsis within a left-sided inguinal hernia sac. J Surg Case Rep \n2014(5):rju046–rju046. https ://doi.org/10.1093/jscr/rju04 6\n 8. Prabhu R, Krishna S, Shenoy R, Thangavelu S (2013) Endome-\ntriosis of extra-pelvic round ligament, a diagnostic dilemma for \nphysicians. BMJ Case Rep. https ://doi.org/10.1136/bcr-2013-\n20046 5\n 9. Breen JL, Neubecker RD. Tumors of the round ligament a \nreview of the literature and a report of 25 cases. Obstet Gynecol. \n1962;19(6)\n 10. Sourial S, Tempest N, K.Hapangama D (2014) Theories on \nthe pathogenesis of malignant tumors. Int J Reprod Med 11(9–\n10):9. https ://doi.org/10.1155/2014/17951 5\n 11. Seydel AS, Sickel JZ, Warner ED, Sax HC (1996) Extrapelvic \nendometriosis: diagnosis and treatment. Am J Surg 171(2):239–\n241. https ://doi.org/10.1016/S0002 -9610(97)89557 -8\n 12. Cervini P, Wu L, Shenker R, O’Blenes C, Mahoney J (2004) \nEndometriosis in the canal of nuck: atypical manifestations in \nan unusual location. Can J Plast Surg 12(2):73–75\n 13. Casparie M, Tiebosch a TMG, Burger G et al (2007) Pathology \ndatabanking and biobanking in The Netherlands, a central role \nfor PALGA, the nationwide histopathology and cytopathology \ndata network and archive. Cell Oncol 29(1):19–24. https ://doi.\norg/10.1155/2007/97181 6\n 14. Pandey D, Coondoo A, Shetty J et al. (2015) Jack in the box: \nInguinal endometriosis. BMJ Case Rep. https ://doi.org/10.1136/\nbcr-2014-20798 8\n 15. Kapan M, Kapan S, Durgun AV, Goksoy E (2005) Inguinal \nendometriosis. Arch Gynecol Obstet 271(1):76–78. https ://doi.\norg/10.1007/s0040 4-004-0624-z\n 16. Boereboom CL, Watson NF, Sivakumar R, Atwal G, Tier -\nney GM (2009) Endometriosis presenting as an acute groin \nswelling: a case report. Cases J 2(1):6438. https ://doi.\norg/10.4076/1757-1626-2-6438\n 17. Husain F, Siddiqui Z, Siddiqui M (2015) A case of endometrio-\nsis presenting as an inguinal hernia. BMJ Case Rep. https ://doi.\norg/10.1136/bcr-2014-20809 9\n 18. Mashfiqul MAS, Chintana CW, Tan YM (2007) Endometrio-\nsis of the inguinal canal mimicking a hernia. Singap Med J \n48(6):e157–e159\n 19. Borghans R, Scheeren C, Dunselman G, Vliegen R (2014) \nEndometriosis of the groin: the additional value of magnetic \nresonance imaging (MRI). JBR-BTR 97(2):94–96\n 20. Catalina-Fernandez I, Lopez-Presa D, Saenz-Santamaria J \n(2007) Fine needle aspiration cytology in cutaneous and sub-\ncutaneous endometriosis. Acta Cytol 51(3):380–384\n 21. Gupta RK (2008) Fine-needle aspiration cytodiagnosis of \nendometriosis in cesarean section scar and rectus sheath mass \nlesions—a study of seven cases. Diagn Cytopathol 36(4):224–\n226. https ://doi.org/10.1002/dc.20797  \n 22. Van Wessem KJP, Simons MP, Plaisier PW (2003) The etiology \nof indirect inguinal hernias: congenital and/or acquired? Hernia \n7(2):76–79. https ://doi.org/10.1007/s1002 9-002-0108-7\n 23. Clausen I, Nielsen KT (1987) Endometriosis in the groin. Int J \nGynecol Obstet 25(6):469–471. https ://doi.org/10.1016/0020-\n7292(87)90064 -6\n 24. Manatakis DK, Stamos N, Agalianos C, Vamvakas P, Kordelas \nA, Davides D (2013) Mesothelial cyst of the round ligament \nmisdiagnosed as irreducible inguinal hernia. Case Rep Surg \n2013(Fig. 2):2–5\n 25. Harper GB, Awbrey BJ, Thomas CG, Askin FB (1986) Meso-\nthelial cysts of the round ligament simulating inguinal hernia. \nReport of four cases and a review of the literature. Am J Surg \n151(4):515–517. https ://doi.org/10.1016/0002-9610(86)90116  \n-9\n 26. Tirnaksiz MB, Erkan A, Dogrul AB, Abbasoglu O (2016) Meso-\nthelial Cysts of the round ligament of the uterus in 9 patients: \na 15-year experience. Int Surg 101(3–4):171–175. https ://doi.\norg/10.9738/INTSU RG-D-15-00159 .1\n 27. Kiyak G, Ergul E, Sarikaya SM, Yazgan A (2010) Endometrio-\nsis of the groin hernia sac: report of a case and review of the \nliterature. Hernia 14:215–217. https ://doi.org/10.1007/s1002  \n9-009-0532-z\n 28. Yang D, Kim H (2010) Sonographic findings of inguinal endo-\nmetriosis. J Ultrasound Med 29:105–110\n\n886 Hernia (2018) 22:881–886\n1 3\n 29. Dunselman GAJ, Vermeulen N, Becker C et al (2014) ESHRE \nguideline: management of women with endometriosis. Hum \nReprod 29(3):400–412. https ://doi.org/10.1093/humre p/det45 7\n 30. Klein AE, Bauer TW, Marks KE, Belinson JL (1999) Papillary \nclear cell adenocarcinoma of the groin arising from endometriosis. \nClin Orthop Relat Res 361:192–198\n 31. Spaczynski RZ, Duleba AJ (2003) Diagnosis of endome-\ntriosis. Semin Reprod Med 21(2):193–207. https ://doi.\norg/10.1055/s-2003-41326","source_license":"public-domain-us","license_restricted":false}