Literature update and MRI case collection of unusual localizations

in this article are included in the article’s Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit h t t p : / / c r e a t i v e c o m m o n s . o r g / l i c e n s e s / b y - n c - n d / 4 . 0 /. Rosaria et al. Discover Medicine (2025) 2:248 https://doi.org/10.1007/s44337-025-00429-z *Correspondence: Valeria Fiaschetti [email protected] 1U.O.C. Diagnostic Imaging, PTV Policlinico “Tor Vergata” University, Viale Oxford 81, Rome 00133, Italy 2Department of Biomedicine and Prevention, University of Rome Tor Vergata, Rome, Italy 3U.O.C. Endocrinology and Diabetology, PTV Policlinico “Tor Vergata” University, Viale Oxford 81, Rome 00133, Italy 4Department of Surgical Sciences, Unit of Obstetrics and Gynecology, University of Rome Tor Vergata, Rome, Italy Literature update and MRI case collection of unusual localizations Meucci Rosaria1, Francesco Garaci2, Valeria Fiaschetti2*, Francesca Montesanto1, Flavia Rufi1, Mario Laudazi2, Colleen Patricia Ryan3, Consuelo Russo4 and Guglielmo Manenti2 1 Introduction Endometriosis is a prevalent gynecologic pathology estimated to affect 10% of women [1] and is defined by the ectopic presence of endometrial tissue outside the uterine cav - ity with consequent recurrent intralesional bleeding and resulting fibrosis. Feldman et al. discerned three forms of pelvic endometriosis: (a) superficial peritoneal lesions; (b) ovarian endometrioma; (c) deep infiltrating endometriosis (DIE), histologically identi - fied as a lesion that extends more than 5 mm into the sub- peritoneal space or involving the walls of pelvic organs and ligaments [ 1]. Preeminent sites for endometriotic lesions include ovaries, pelvic peritoneum, uterosacral ligaments, and torus uterine [ 2]. Atypi- cal pelvic endometriosis localizations can occur in the cervix, vagina, round ligaments, ureter, and nerves. Moreover, rare extra pelvic endometriosis implants can be localized in the upper abdomen, subphrenic fold or in the abdominal wall. While characteristic symptoms comprise secondary dysmenorrhea and cyclic or persistent pelvic pain, the diagnostic context is often non-specific, contributing to a notable diagnostic delay of up Discover Medicine

Endometriosis affects approximately 10% of women of reproductive age and is a significant cause of pelvic pain and infertility. It manifests in three patterns: superficial peritoneal lesions, ovarian endometriomas, and deep infiltrating endometriosis (DIE). Our aim is to remind radiologists of the possibility of atypical locations of pelvic and extrapelvic endometriosis and to illustrate their characteristics on magnetic resonance imaging (MRI). The most common site of endometriosis is the ovaries, followed by the pelvic peritoneum. Less common locations include deep subperitoneal tissues, the gastrointestinal tract, the bladder, the thorax, and subcutaneous tissues. We present three rare clinical cases: diaphragmatic endometriosis, inguinal canal endometriosis, and a case of sciatic nerve infiltration. MRI provides important findings that help classify the disease and identify the extent of the lesion, thus facilitating appropriate diagnosis and treatment. Radiologists should be familiar with the MRI findings of DIE in various anatomical sites to provide information that allows for adequate pre-surgical counseling. Page 2 of 14 Rosaria et al. Discover Medicine (2025) 2:248 to 10 years [1– 3]. Unusual sites of endometriosis may be associated with specific symp - toms depending on different localizations [4]. Extra pelvic compartments include right bowel structures (cecum, ileum, and appen - dix), sigmoid colon, lumbopelvic ureter, abdominal wall as well as umbilicus, and external part of inguinal canal [ 5], diaphragm and this paper explores three rare endo - metriosis localizations, highlighting their Magnetic Resonance Imaging (MRI) and clini - cal features in cases involving the sciatic nerve, diaphragm, and abdominal wall. 2 Non-invasive diagnosis of endometriosis 2.1 The role of MRI and MRI features MRI is a useful noninvasive tool used to diagnose endometriosis because of the absence of ionizing radiation, multiplanar projections, and high contrast resolution with high sensitivity for detection of hemorrhagic lesions [6]. According to European Society of Urogenital Radiology (ESUR), the paramount indi - cation for MRI lies in the examination of DIE. ESUR further advocates for MRI utili - zation in cases marked by positive clinical features but negative ultrasonography (US) results, as well as in presurgical planning and as a second-line test when US proves inconclusive [ 2– 7]. MRI is essential in preoperative decision making, particularly in cases of extrapelvic disease where first line imaging by expert operators is not accurate [5]. Several papers demonstrated high agreement between imaging and surgical findings [8– 9]. This is also mentioned in the recent ESHRE guidelines [ 10], which highlight that surgery is no longer the gold standard to diagnose endometriosis and MRI can be used for consequent patient management. In 2003–2005, SEF (Stiftung Endometriose-Forschung; Scientific Endometriosis Foun - dation) published the ENZIAN classification, which established a useful tool for DIE classification focused also on MRI [ 11]. The latest revision of the ENZIAN score (2020) proposes a new comprehensive classification system, which includes anatomical location and size of the different forms of endometriotic lesions, presence of adhesions, and the degree of involvement of adjacent organs [12]. On MRI, DIE manifests as hemorrhagic cysts or plaques, exhibiting hyperintensity in T1-weighted sequences, as well as solid or fibrous lesions characterized by low signal intensity on both T1- and T2-weighted images, indicative of an infiltrating behavior. High-resolution T1 and T2-weighted images are employed for meticulous evaluation, particularly when lesions involve ligaments and the subperitoneal space (> 5 mm under peritoneal serosa). Discrimination between endometriotic tissue with hemorrhagic con - tent and fibrosis is achievable through MRI [3– 13]. In advanced stages, endometriosis is often associated with adhesions, appearing as spiculated bands of low to intermediate signal intensity on T1- and T2-weighted imag - ing. These adhesions can obscure the interfaces between organs, leading to atypical imaging characteristics such as peritoneal space obliteration, fixed fluid accumulations, and distortion or displacement of nearby organs. To enhance visualization, axial, cor - onal, and sagittal planes are typically used, with oblique planes aligned to the affected organs providing additional information [2]. Page 3 of 14 Rosaria et al. Discover Medicine (2025) 2:248 2.2 MRI acquisition protocols As described above endometriosis is a multifocal and systemic disease and MRI allows complete evaluation of every abdominal compartment, identifying and mapping all types of endometriosis lesions within a single study [5]. Regarding technical recommendations, the application of fat saturation is advised for enhanced precision. Chemical frequency-selective fat saturation, targeting fat tissue, proves instrumental in accentuating distinctions among non-fat T1-weighted hyper - intense structures, thereby amplifying the visibility of minute hemorrhagic lesions associated with endometriosis [ 2]. Recent ESUR guidelines do not provide specific rec - ommendations regarding the timing of MRI in relation to the menstrual cycle [ 7]. At our institution, MRI was acquired with high field-strength (3 Tesla) systems, acquisition of axial, coronal and sagittal T2-weighted images and spin-echo or gradient-echo axial T1-weighted images obtained with or without fat suppression, with a slice thickness of 3 mm. In selected and atypical cases, axial T1-weighted images were obtained after intravenous administration of gadolinium-based contrast agent when deemed beneficial for diagnosis. The usefulness of intravenous gadolinium injection to characterize endo - metriosis is still under discussion. Incidentally, international recommendations assert that the utilization of contrast agents typically does not contribute substantially to the initial diagnostic information [14]. Nevertheless, it is deemed mandatory in cases where malignant transformation of endometrioma is suspected, as highlighted by Schneider at al. [14]. MRI with vaginal opacification using sonographic gel is recognized as a viable option for evaluating DIE. Some papers recommended MRI with gel opacification of vagina for studying usual localization of DIE, particularly for the added value in evalu - ation of recto-vaginal septum, utero-sacral ligaments and posterior vaginal fornix [ 15]. It’s important to note that in our recent practice, we refrain from the practice of distend- ing the vagina with sonographic gel [6]. 3 Unusual locations of extragenital endometriosis Extragenital endometriosis encompasses a spectrum of rare but clinically significant lesions that extend well beyond the pelvis, affecting organs and tissues such as the kidney, thoracic cavity, diaphragm, abdominal wall and groin [ 16– 28]. Although each location accounts for a small fraction of all endometriotic cases, their diverse presen - tations—including flank pain mimicking renal carcinoma, catamenial pneumothorax, cyclical chest or shoulder pain, and palpable masses in surgical scars—pose substantial diagnostic and therapeutic challenges. Early recognition and accurate imaging assess - ment (primarily with MRI) are therefore essential to distinguish these lesions from malignancy, plan optimal surgical management and minimize morbidity. Patients with thoracic endometriosis (TE) usually present with the triad of pain, pneu - mothorax and haemoptysis [ 19]. While CT primarily serves to exclude other causes of pleural or parenchymal pathology, MRI more directly demonstrates endometrial implants: small pleural or parenchymal nodules, haemothorax or haemorrhagic effu - sions appear hyperintense on T1- weighted fat -sat sequences and often enhance as discrete nodules or thickened pleural areas. MRI’s overall sensitivity for detecting dia - phragmatic and pleural disease approaches 83% [20, 51]. Diaphragmatic endometriosis (DE) refers to endometriotic implants encountered on the visceral (abdominal) side of the diaphragm and it could be associated with TE. It is Page 4 of 14 Rosaria et al. Discover Medicine (2025) 2:248 rare and forms 0.67–4.7% of all endometriosis cases [ 21– 22, 52]. DE could cause symp - toms like cyclic or noncyclic shoulder, arm, chest, or upper quadrant abdominal pain, but it is most frequently diagnosed incidentally during laparoscopic surgery for coex - isting pelvic endometriosis. These foci are hyperintense on T1- weighted fat-sat images and demonstrate heterogeneous signal (“shading”) on T2; contrast-enhanced sequences reveal small enhancing nodules, aiding in differentiation from fibrotic or benign thickenings. Renal involvement in endometriosis is exceedingly rare—accounting for under 1% of cases—but can mimic malignancy with presentations of flank pain, haematuria and even a palpable renal mass [ 16]. In case of symptoms, MRI is mandatory, to clarify the extent of the lesion and the depth of lesion invasion and to plan adequate surgical treatment [17– 18] Typical MRI features include cystic or mixed cystic-solid lesions that are mark - edly hyperintense on T1- weighted fat-saturated sequences (reflecting blood products), exhibit variable “shading” on T2- weighted images (due to chronic haemorrhage), and show peripheral or septal enhancement after gadolinium administration. Abdominal wall endometriosis is divided into parietal and visceral endometriosis. Pari- etal endometriosis lesions involve primary lesions on abdominal wall (often iatrogenic, as for scar endometriosis after caesarean section or umbilical endometriosis after lapa - roscopic surgery), groin and perineum [ 23– 24]. Visceral abdominal wall implants follow the same signal characteristics but are located along peritoneal surfaces of omentum or bowel serosa. On MRI, these appear as well-circumscribed masses within subcutane - ous fat or muscle. The frequency of abdominal wall endometriosis has been estimated to be 0.04-5.5%, and symptoms could include a palpable mass (99%), cyclic pain (71%) and cyclic bleeding [25]. Umbilical endometriosis can be categorized into two types: secondary umbilical endo - metriosis, which is believed to arise from iatrogenic causes at the port site following laparoscopic surgery, and primary umbilical endometriosis, which occurs spontaneously without any history of surgical procedures [ 25– 26]. Notably, primary umbilical endo - metriosis is more commonly observed compared to the secondary form [ 27]. Imaging cannot reliably distinguish primary from secondary forms, so clinical history remains crucial. Inguinal endometriosis is a very unusual extrapelvic site for endometriosis (estimated incidence < 0.1% of cases) [ 28]. There is an increased right-sided predilection (~ 85% of reported cases) [ 29] likely due to the theory of menstrual blood reflux into the pelvic cavity [30]. It can present in various forms, such as cystic lesions within the hernia sac or the Nuck’s canal, as well as solid masses located in the extra-pelvic round ligament or subcutaneous tissue. Clinically, it is identified by the presence of a groin mass, which may be associated with pain and periodic flare-ups or, alternatively, may be painless but accompanied by cyclical menstrual symptoms. 4 Cases presentation 4.1 Case 1: upper abdomen diaphragm localization 4.1.1 Clinical case We present a case of a 36-year-old woman with history of known fibrotic pelvic endo - metriosis extended to the torus, uterosacral ligaments and round ligaments. Intestinal adhesions were also present. With the intention of achieving pregnancy, the patient Page 5 of 14 Rosaria et al. Discover Medicine (2025) 2:248 stopped estrogenic-progestin therapy. Few months after interrupting estrogenic-proges- tin therapy, the patient developed dysmenorrhea and pain radiating to the right shoulder during the menstrual cycle. Physicians hypothesized disease recurrence and therefore decided to perform an MRI exam extended to the upper abdomen. The suspicion of dia - phragmatic localization was accurate. Indeed, T1-weighted sequences revealed a focal hyperintensity in the right diaphragmatic pillar, adjacent to the seventh hepatic segment. This finding raised suspicion of a deep endometriotic nodule, measuring approximately 9 × 2 mm (Fig. 1). A diagnosis of fibrotic DIE with associated extra-pelvic endometriotic plaque in active phase was made. 5 Discussion DE involving the full thickness of the diaphragm includes 1-1.5% of patients diagnosed with endometriosis [ 31]. Preoperative diagnosis of DE poses various challenges due to the significant proportion of asymptomatic patients, limited sensitivity of existing imag - ing techniques, and lack of clinical suspicion [ 21]. Remarkably, as many as 70% of indi - viduals with DE exhibit no discernible symptoms [ 21]. This uncommon condition may remain asymptomatic and can be discovered incidentally [31]. When symptomatic, DE is typically associated with chest pain (often pleuritic and pre- dominantly on the right side), dyspnea, epigastric discomfort, shoulder pain, and upper abdominal pain, which frequently occurs abruptly. The pain results from irritation of the sensory branches of the C3 and C5 nerve roots. Symptom severity depends on the depth and location of the lesions and is commonly linked to cyclical hormonal changes during the menstrual cycle [31– 32]. DE predominantly affects the right side, with lesions commonly located in the anterior or posterior diaphragm and in the area behind the liver. The higher prevalence in the subphrenic region is explained by the retrograde menstruation theory, suggesting that refluxed endometrial tissue becomes trapped by the falciform ligament near the right side of the diaphragm. MRI plays a crucial role in detecting these lesions, which are primarily visualized as hyperintense nodules on fat-suppressed T1-weighted sequences. According to Rousset et al., MRI offers a sensitivity of 78–83% for identifying these abnormalities [ 33]. The authors suggest that a report of lesions of extrapelvic endometriosis should be characterized and described like pelvic localizations. Extrapelvic endometriosis nodules can be defined based on shape and size: • Foci: Thin and superficial, less than 1 cm. • Nodules Solid: tri-dimensional, more than 1 cm. • Plaques Fibrotic: bi-dimensional, more than 3 cm. Superficially Isolated lesions usually measure less than 5  mm, without infiltration of muscularis mucosa. Depth of invasion divides deep endometriosis from superficial: more than 5  mm with infiltration of muscularis or full thickness with total diaphrag - matic infiltration [ 21– 34]. Very often MRI alone is not sufficent and staging remains surgical. The management of diaphragmatic or suspected thoracic endometriosis often relies on the patient’s medical history. For asymptomatic cases of DE, an expectant approach is strongly recommended as the most suitable treatment option compared to other Page 6 of 14 Rosaria et al. Discover Medicine (2025) 2:248 interventions [ 35]. For symptomatic individuals, surgical intervention is considered effective, particularly when hormonal therapies have not provided relief [36− 22]. The variables considered choosing the set therapy are patient age, future fertility desire, symptomatic status, disease extension and location. In literature Smith et al. sug - gest surgery in symptomatic and infertile patients with failure of medical treatment [21]. In our case, the patient had a “focus” of deep DE, however without full thickness infiltration of muscle. Our patient had minor symptoms with a low risk of developing Fig. 1 Diaphragm localization; a-b: T1FS sequences coronal and axial plane of upper abdomen shows hyperin - tense linear area at the level of the right diaphragmatic pillar (diameter of approximately 9 millimeters); findings compatible with active haemorrhagic endometriotic plaque Page 7 of 14 Rosaria et al. Discover Medicine (2025) 2:248 complications, more over the plaque was single and small (< 1 cm). Our patient under - went continuous hormonal progestin-based therapy, with consequent amenorrhea. After six months, the symptoms improved. Dysmenorrhea transitioned to amenorrhea and the irradiating pain to the shoulder almost completely disappeared. 5.1 Case 2: posterior lateral compartment sciatic nerve localization 5.1.1 Clinical case We present a case of a 43-year-old woman, affected by DIE, who had a known history of ovarian endometriosis and complained of right sciatic pain, which was more evident during the menstrual cycle. She underwent lumbo-sacral MRI which did not show sig - nificant spinal abnormalities, such as vertebral collapses or discal hernias. Due to the catamenial progression of the symptoms the physician supposed an atypical localization of endometriosis, the patient underwent TVUS that showed bilateral endometriomas and a plaque of DIE in the posterior compartment. The lesions described at TVUS did not fully explain the symptoms, so she also underwent a pelvic MRI to better evaluate all pelvic compartments. The MRI examination identified suspicious lesions at the right ischial foramen, within the iliac obturator vascular-nervous bundle. It revealed a nodular region with spiculated margins measuring 25  mm in diameter, exhibiting non-homogeneous intensity. This variability was attributed to the presence of small hyperintense areas on T1-weighted imaging, indicative of haemorrhagic content (Fig. 2). This finding, suggestive of an active DIE plaque, also appears to involve the root of the ischial nerve. We concluded the MRI report describing a condition of endometriosis Fig. 2 Sciatic nerve localization; a–b: axial T1FSw and T2w sequences, c: zoomed coronal T2w sequence highlight- ing the suspicious nodule. MRI show an endometriotic plaque infiltrating the extra pelvic portion of the right ischi- atic nerve, hyperintense on the T1w sequences and with very low T2 signal, compatible with active localization of extra-genital endometriosis in the lateral compartment Page 8 of 14 Rosaria et al. Discover Medicine (2025) 2:248 affecting both intra-pelvic median and posterior compartment and extrapelvic lateral compartment, involving the right sciatic nerve near the ipsilateral sciatic foramen. Our patient underwent surgical laparoscopic approach with excision of posterior DIE and nerve sparing surgery to remove the sciatic nodule. Histological findings confirmed sciatic nerve endometriosis. The symptoms resolved after surgical treatment and the patient started continuous progestin-based hormonal treatment to avoid disease relapse. 6 Discussion The sciatic nerve, the largest somatic nerve in the human body, was first linked to cycli - cal sciatica in a case reported by Head et al. in 1962 [ 37]. The exact mechanism behind the sciatic localization of endometrial cells remains unclear. One theory suggests migra - tion of endometrial cells from pelvic endometriotic lesions, while other hypotheses pro - pose mechanisms such as hematogenous spread, coelomic metaplasia, or embryonic cell remnants [37– 39]. Additionally, Possover et al. introduced a “neurologic hypothesis” in 2007, describing a case of isolated sciatic nerve endometriosis with no detectable pelvic endometriotic lesions [40]. The most frequent site of sciatic nerve involvement in endometriosis is near the greater sciatic foramen, with the right sciatic nerve being more commonly affected than the left as seen in other reports [ 41, 54]. Cyclical bleeding into adjacent tissues leads to inflammation, fibrosis and scarring, which exacerbate nerve compression over time. The diagnosis of sciatic nerve endometriosis is based on clinical symptoms and imag - ing studies, with histopathological examination providing definitive confirmation. Key clinical indicators include sciatica that follows a cyclical pattern related to menstruation. As the condition progresses, pain-free intervals shorten, and the pain becomes persis - tent, though it continues to worsen during menstruation. MRI is the preferred imaging modality for detecting sciatic endometriosis, offer - ing a sensitivity of 90% and a specificity of 98% [ 42]. The appearance of endome - triotic lesions varies with the stage of hemorrhage, typically showing high signal intensity on T1-weighted images and a combination of high and low signal intensities on T2-weighted images. Importantly, the absence of pelvic endometriosis does not rule out sciatic nerve involvement [43]. Surgical treatment depends on the extent of the disease. If only the pelvic portion of the sciatic nerve is affected, a skilled gynecologist can perform a laparoscopic or robotic procedure [44]. When the extra-pelvic portion or both pelvic and extra-pelvic parts of the nerve are involved, a trans-gluteal surgical approach is required. In such cases, a multidisciplinary team comprising neurosurgeons and orthopedic specialists is essential [45]. In conclusion, sciatic nerve endometriosis should be considered in patients presenting with sciatica exhibiting a cyclical pattern. MRI serves as the optimal imaging modality to support clinical diagnosis. Treatment requires the involvement of a multidisciplinary surgical team with a thorough understanding of retroperitoneal neuroanatomy. The choice of surgical approach, whether laparoscopic or trans-gluteal, should be carefully planned prior to the procedure. Early diagnosis, timely intervention, and comprehen - sive post-operative physiotherapy can significantly enhance recovery outcomes for these patients. Page 9 of 14 Rosaria et al. Discover Medicine (2025) 2:248 6.1 Case 3: abdominal wall and inguinal endometriosis 6.1.1 Clinical case A 44-year-old patient presented with heavy menstrual periods. The patient had experi - enced two spontaneous pregnancies and deliveries and presented with a current medical history of systemic lupus erythematosus under treatment. At the first clinical evaluation, she complained of dysmenorrhea (Visual Assessment Score, VAS 9), dyspareunia (VAS 7), with no dyschezia or dysuria. She also complained of severe pain (VAS 10) in the right inguinal region during menstrual phase. She had never taken hormonal treatment. Because of these invalidating symptoms, she underwent TVUS which showed a glo - bose uterus presenting fibromatosis and direct signs of adenomyosis. An hypoechoic nodule of 10 × 9 × 4 mm in size at the level of the torus uteri and an analogous nodule of 15 × 8 × 9 mm in size in the posterior vaginal fornix were detected. Ovaries were normal. In the right inguinal region, a painful hypoechoic nodule of 39 × 14  mm in size, with irregular margins, moderately vascularized at color-Doppler US, was observed. All these findings led to the suspicion of pelvic DIE. The probability of an extra-pel - vic endometriosis, as inguinal endometriosis localization, was high and an indication to carry out an MR exam was given. She was referred to dedicated genitourinary specialist radiologist. The MRI was performed with T1 fat saturation and T2 sequences in axial, coronal and sagittal planes without contrast medium (Fig. 3). MRI showed an ovoid mass localized in the anterior abdominal wall which infiltrated the edge of the rectus abdomi - nis muscle and extended to the wall of right inguinal canal with probable involvement of the pubic nerve as hypothesized from clinical symptoms. The MR images and features, in accordance with TVUS, were suggestive of endometrial glands ectopic localizations as glandular-cystic plaque. Based on the absence of previous surgery, clinical symptoms, US and MRI features, the diagnostic hypothesis was Nuck’s canal endometriosis (Fig.  4). After diagnosis, the patient started a continuous progestin-based hormonal treatment for 12 months, induc - ing amenorrhea, with improvement of dysmenorrhea but with persistence of dyspa - reunia and inguinal pain. Due to the persistence of symptoms the patient underwent laparoscopy to remove DIE and groin incision to remove inguinal endometriosis. At follow-up, symptoms were reduced (dysmenorrhea VAS 5, dyspareunia VAS 4, and absent inguinal pain). 7 Discussion Endometriosis of the inguinal region may involve inguinal hernia sac, Nuck’s canal, uter- ine round ligament (RLU) and subcutaneous tissue [46– 47]. Inguinal endometriosis (from the labia majora to the abdominal wall) is a rare extra - pelvic site for endometriosis, with incidence < 0.1% [48]. Incomplete obliteration of the Nuck’s canal is known as a patent processus vaginalis and can result in either an inguinal hernia or a hydrocele in female children. It can provide a pathway for superficial ingui - nal endometriosis [ 49]. RLUs have an intrapelvic and an extrapelvic portion where the extrapelvic one is the distal part of the ligament in the Nuck’s canal [ 2]. Endometriosis from RLUs may advance through the inguinal ring into the inguinal canal, and this may be an anatomical pathway for endometrial implants to the superficial inguinal soft tis - sues [50]. Symptoms of endometriosis of the intrapelvic portion of the RLUs are non - specific, usually referred as pain localized in the lower abdomen [ 2]. Our patient had Page 10 of 14 Rosaria et al. Discover Medicine (2025) 2:248 severe groin pain during menstrual cycle, associated with superficial swelling at the right inguinal level. On sonographic imaging, our patient had a solid (hypoechoic) nodule, with irregu - lar margins, moderately vascularized on color doppler. Nevertheless, the sonographic appearance of inguinal endometriosis is not typical, varying between a predominantly Fig. 3 Abdominal wall localization; a–b: T1FS- and T2FS -weighted axial sequences; c–d: T1FS- and T2-weighted sagittal sequences. MR images show an ovoid mass localized in the abdominis wall region which infiltrates the edge of the abdominis rectus muscle (a–b) and the anterior wall of inguinal canal (c–d). On T1-weighted sequenc- es (a, c) the lesion is isointense to the muscle. On T2-weighted sequences (c, d), the lesion displays areas of mixed hypointensity and hyperintensity, consistent with endometrial glands Page 11 of 14 Rosaria et al. Discover Medicine (2025) 2:248 solid, a cystic or combined mass [ 50]. When extra-pelvic endometriosis is suspected, the integration of US and MRI, like in our case, is the best approach in the diagnostic workup [2, 5, 50]. Differential diagnosis includes abdominal wall masses, such as her - nias, lipomas, sebaceous cysts hematomas, and malignant tumors [ 2]. Our patients underwent first-line medical treatment and subsequently surgery. As suggested by Delkalitsis et al., while other treatment modalities like hormonal suppres - sive therapy remain to be evaluated, surgical treatment consists of excision of the mass from the Nuck’s canal and subcutaneous lesions is the better choice in case of severe symptoms [50, 53]. 8 Conclusion The most recent guidelines and reviews confirm the pivotal role of MRI both in the preoperative assessment and in the follow-up of extrapelvic localizations [ 55– 56]. The diagnostic role of MRI in endometriosis is evolving, requiring radiologists to develop a comprehensive understanding of various clinical and imaging manifestations in both typical and atypical locations. This is particularly crucial when assessing patients sus - pected of DIE. Radiologists must diligently explore, document, and stratify the disease across a spectrum of locations in endometriosis patients. Accurate diagnosis holds para - mount significance for steering appropriate patient management. While laparoscopy remains the benchmark for endometriosis diagnosis, certain diagnostic challenges exist, such as the potential oversight of nodules concealed by adhesions and subperitoneal dis- ease, highlighting the essential role of imaging. Successful treatment strategies encompass hormonal-based therapies including com - bined oral contraceptives (COC), progesterone agents, alongside lesion removal with radical surgery. In instances where surgery is indicated, MRI serves as a valuable tool, providing a comprehensive roadmap. This facilitates effective presurgical counseling and guides the surgeon in the meticulous eradication of all endometriotic implants. The inte- gration of MRI into the diagnostic and therapeutic framework enhances precision and contributes significantly to the overall management of endometriosis. Fig. 4 Canal of Nuck localization. a–b: respectively T2-weighted axial and sagittal MR images show the same le - sion as Fig. 3 closely adherent to the right inguinal region suspicious for Nuck’s canal endometriosis Page 12 of 14 Rosaria et al. Discover Medicine (2025) 2:248 Author contributions All authors contributed equally to the work. The tasks were divided as follows: F.R, F.M and C.R wrote the main manuscript text under the supervision of R.M and V.F, radiologists with over 10 years of experience in diagnostic imaging of the female pelvis.C.P .R. Conducted multiple ongoing reviews of the manuscript with particular attention to scientific terminology and English language.M.L prepared Figs. 1, 2, 3 and 4 and conducted multiple ongoing reviews and reviesed article layout and references F.G and G.M conducted the final review. Funding the authors did not receive support from any organization for the submitted work. Conflict of interest: the authors have no conflicts of interest to declare that are relevant to the content of this article. Data availability As per the Ministerial Decree of February 14, 1997, all MRI images of the reported cases will be stored in the digital archive of our polyclinic for 10 years.The clinical data collected will be gathered by the Research Center and processed there. The Data Protection Officer for the healthcare company can be contacted upon reasonable request.Informed consent was obtained from all individual participants included in the study. The informed consents will be archived in the archive of our polyclinic as per Law No. 219 of December 22, 2017. Declarations Ethical approval and Consent to participate The research was carried out following the guidelines of the institutional ethics committee. In particular, the need for ethical approval was waived off by the ethical committee because our study is a case series and we iconographically describe images acquired during routine MRI examinations. The study was performed in accordance with the ethical standards as laid down in the 1964 Declaration of Helsinki and its later amendments or comparable ethical standards. Informed consent was obtained from all individual participants included in the study. Informed consent The patient(s), or their next of kin, or their legal representative(s) signed: - written informed consent in Italian for the performance of contrast-enhanced MRI. - written informed consent in Italian to the use of images for research purposes and scientific description with written informed consent forms as approved by our ethical committee. The privacy of the patient has been assured in all materials. Written informed consent forms from the patient(s) and/or their legal representative(s)/guardian(s) are preserved in our department archive (U.O.C. Diagnostic Imaging, PTV Policlinico “Tor Vergata” University, Viale Oxford 81, 00133, Rome, Italy). Consent to publish The authors affirm that human research participants provided informed consent for publication. Competing interests The authors declare no competing interests. All procedures performed in studies involving human participants were in accordance with the ethical standards of the institutional research committee and with the 1964 Helsinki Declaration and its later amendments or comparable ethical standards. Received: 6 December 2024 / Accepted: 12 July 2025

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