Three-dimensional CT vascular mapping of a juxtauterine pelvic schwannoma suggesting retroperitoneal origin: a case report.

A 54-year-old perimenopausal woman (gravida 3, para 2) was referred for evaluation of a pelvic mass detected during a routine health checkup. Her last menstrual period had occurred 4 months before presentation. She had no significant medical history. Pelvic examination revealed an approximately 10 cm mass on the left side of the uterus with limited mobility. Rectal examination demonstrated preserved mobility between the tumor and rectum. The cervix was displaced by the tumor, and the external cervical os could not be clearly identified. Transvaginal ultrasonography demonstrated an 11.3 cm mass extending from the left side of the uterus into the pouch of Douglas. Contrast-enhanced MRI demonstrated a well-circumscribed mass measuring approximately 10 cm, broadly abutting the left lateral wall of the cervix and displacing the uterus to the right. The mass was predominantly cystic and showed high signal intensity on T2-weighted images with thick reticular septa. It appeared hypointense on T1-weighted images. Contrast enhancement was observed along the septa. Both ovaries were identified separately from the tumor and appeared normal, and no endometrial abnormalities were observed ( Fig. 1 ). Fig. 1 Pelvic MRI. (A, B, D) T2-weighted MRI and (C) gadolinium-enhanced T1-weighted MRI demonstrating a large heterogeneous pelvic mass adjacent to the uterus. The tumor showed predominantly high T2 signal intensity with internal cystic and degenerative changes. The uterus (yellow arrows) was compressed and displaced by the mass; however, clear separation between the tumor and uterus could not be identified on MRI alone, making exclusion of a uterine origin difficult. In panel D, the left ovary was identified separately (purple circle), suggesting a non-adnexal pelvic tumor. (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.) Fig. 1 Pelvic MRI. (A, B, D) T2-weighted MRI and (C) gadolinium-enhanced T1-weighted MRI demonstrating a large heterogeneous pelvic mass adjacent to the uterus. The tumor showed predominantly high T2 signal intensity with internal cystic and degenerative changes. The uterus (yellow arrows) was compressed and displaced by the mass; however, clear separation between the tumor and uterus could not be identified on MRI alone, making exclusion of a uterine origin difficult. In panel D, the left ovary was identified separately (purple circle), suggesting a non-adnexal pelvic tumor. (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.) Based on these findings, benign mesenchymal tumors, including degenerated leiomyoma, neurogenic tumor, and solitary fibrous tumor, were considered; however, the organ of origin could not be determined. No definite continuity with major pelvic nerves was identified on imaging. To evaluate the feeding vessels and anatomical relationship with the left ureter, contrast-enhanced multidetector CT was performed, and preoperative three-dimensional reconstruction images of the tumor and surrounding anatomy using SYNAPSE VINCENT software were generated. Arterial- and venous-phase images obtained 40 and 150 s after contrast injection demonstrated that the tumor was not supplied by direct branches from the uterine artery but was instead supplied by two direct branches of the internal iliac artery ( Fig. 2 ). These findings suggested a retroperitoneal tumor supplied by branches of the internal iliac artery rather than a uterine tumor. The left ureter was displaced by the tumor, although no hydronephrosis was observed. Laboratory findings were within normal limits (hemoglobin, 12.2 g/dL; CEA, 1.4 ng/mL; CA125, 8 U/mL; LDH, 146 U/L). Fig. 2 Contrast-enhanced CT and three-dimensional vascular reconstruction. (A) Arterial-phase contrast-enhanced CT demonstrating displacement of the uterus without definitive continuity between the uterus and tumor. (B, C) Three-dimensional reconstructed images generated using SYNAPSE VINCENT (© Fujifilm Medical). The uterine artery (yellow arrows) coursed around the tumor without supplying feeding vessels to the mass, arguing against a pedunculated subserosal leiomyoma. (D) Feeding vessels arising from branches of the internal iliac artery, including the lateral sacral artery (blue arrows), were identified, suggesting a retroperitoneal origin of the tumor. (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.) Fig. 2 Contrast-enhanced CT and three-dimensional vascular reconstruction. (A) Arterial-phase contrast-enhanced CT demonstrating displacement of the uterus without definitive continuity between the uterus and tumor. (B, C) Three-dimensional reconstructed images generated using SYNAPSE VINCENT (© Fujifilm Medical). The uterine artery (yellow arrows) coursed around the tumor without supplying feeding vessels to the mass, arguing against a pedunculated subserosal leiomyoma. (D) Feeding vessels arising from branches of the internal iliac artery, including the lateral sacral artery (blue arrows), were identified, suggesting a retroperitoneal origin of the tumor. (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.) Open surgery was selected because retroperitoneal origin and involvement of major pelvic vessels could not be excluded preoperatively. Surgery was performed 4 weeks after the initial visit. Considering the patient's perimenopausal status and the need to secure an adequate operative field, total hysterectomy with bilateral salpingo-oophorectomy was performed in addition to tumor resection. A ureteral stent was inserted intraoperatively to reduce the risk of ureteral injury. At laparotomy, a 10 cm tumor was identified within the left retroperitoneal space adjacent to the uterus. After entering the retroperitoneal space, the ureter was identified running directly over the tumor and was carefully dissected free. The bladder was then dissected away from the uterus and tumor, allowing mobilization of the tumor and uterus en bloc. Guided by the preoperative 3D reconstruction images, the left uterine artery was identified and ligated as part of the hysterectomy procedure. No feeding vessels from the uterine artery to the tumor were observed, allowing the uterine artery to be separated easily from the tumor. The feeding arteries arising from the internal iliac artery were identified and coagulated. The tumor was completely resected en bloc with the uterus ( Fig. 3 ). The arterial supply corresponded well with the preoperative imaging findings; however, multiple venous branches draining into the internal iliac vein were encountered intraoperatively, and injury to the internal iliac vein occurred, requiring continuous suturing for hemostasis. Fig. 3 Intraoperative findings and gross specimen. (A) After transection of the bilateral round ligaments and infundibulopelvic ligaments, no apparent continuity was observed between the tumor (yellow arrow), uterus, or bilateral adnexa, confirming a retroperitoneal location. (B) The uterine artery (white arrow) was identified adjacent to the tumor and ligated. No direct feeding vessels from the uterine artery to the tumor were observed, consistent with the preoperative vascular assessment. (C) The ureter was displaced by the tumor and identified near the tumor margin (blue arrow). The ureter was carefully mobilized laterally, and the tumor was successfully resected without ureteral injury. (D) Resected specimen showing the retroperitoneal tumor (yellow arrow) adjacent to the uterus and bilateral adnexa. (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.) Fig. 3 Intraoperative findings and gross specimen. (A) After transection of the bilateral round ligaments and infundibulopelvic ligaments, no apparent continuity was observed between the tumor (yellow arrow), uterus, or bilateral adnexa, confirming a retroperitoneal location. (B) The uterine artery (white arrow) was identified adjacent to the tumor and ligated. No direct feeding vessels from the uterine artery to the tumor were observed, consistent with the preoperative vascular assessment. (C) The ureter was displaced by the tumor and identified near the tumor margin (blue arrow). The ureter was carefully mobilized laterally, and the tumor was successfully resected without ureteral injury. (D) Resected specimen showing the retroperitoneal tumor (yellow arrow) adjacent to the uterus and bilateral adnexa. (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.) Operative time was 5 h and 4 min, and estimated blood loss was 2085 mL. Six units of packed red blood cells and six units of fresh frozen plasma were transfused perioperatively. The ureteral stent was removed at the end of the procedure. The patient had no postoperative complications, was discharged on postoperative day 6, and was asymptomatic without evidence of recurrence at 4-month follow-up. Histopathological examination demonstrated spindle cell proliferation with marked hyalinization and cystic degeneration, nuclear palisading, and Verocay bodies. Immunohistochemistry revealed positivity for S-100 and SOX10, confirming the diagnosis of schwannoma ( Fig. 4 ). Fig. 4 Histopathological findings. (A) Hematoxylin and eosin (H&E) staining (×200) showing nuclear palisading and Verocay bodies (blue arrow), as well as cystic degeneration (yellow arrow). (B) H&E staining (×100) showing spindle cell proliferation with marked hyalinization (blue arrow) and cystic degeneration (yellow arrow). (C, D) Immunohistochemical staining (×200) demonstrating diffuse positivity for S-100 (C) and SOX10 (D), consistent with the diagnosis of schwannoma. (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.) Fig. 4 Histopathological findings. (A) Hematoxylin and eosin (H&E) staining (×200) showing nuclear palisading and Verocay bodies (blue arrow), as well as cystic degeneration (yellow arrow). (B) H&E staining (×100) showing spindle cell proliferation with marked hyalinization (blue arrow) and cystic degeneration (yellow arrow). (C, D) Immunohistochemical staining (×200) demonstrating diffuse positivity for S-100 (C) and SOX10 (D), consistent with the diagnosis of schwannoma. (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.)

This work was supported by 10.13039/501100001691 JSPS KAKENHI Grant Number JP24K12551 .

Written informed consent was obtained from the patient for the publication of the case report and accompanying images.

In pelvic masses adjacent to the uterus that are difficult to distinguish from subserosal leiomyomas on MRI, retroperitoneal tumors should be considered, particularly when both ovaries appear normal. Although 3D vascular mapping using contrast-enhanced CT cannot provide a histological diagnosis, it may serve as a useful adjunct for estimating the organ of origin and facilitating individualized surgical planning.

This case highlights the potential usefulness of evaluating tumor-feeding vessels using contrast-enhanced CT with 3D reconstruction to estimate the organ of origin and facilitate surgical planning when physical examination, ultrasonography, and MRI alone are insufficient. In pelvic masses adjacent to the uterus with normal-appearing ovaries, differential diagnosis should consider both the organ of origin and histological type. Possible sites of origin include the uterus, gastrointestinal tract, retroperitoneum, and pelvic wall. Histological differential diagnoses include leiomyoma, leiomyosarcoma, gastrointestinal stromal tumor, schwannoma, solitary fibrous tumor, lymph node lesions, lipomatous tumors, and paraganglioma. Although MRI is the first-line imaging modality for pelvic tumors, it may not always allow accurate determination of either the organ of origin or histological type [2] . In the present case, contrast-enhanced CT combined with 3D reconstruction enabled estimation of the tumor origin and facilitated surgical planning. The absence of feeding branches from the uterine artery and the presence of direct branches from the internal iliac artery suggested a retroperitoneal origin. Furthermore, there was good agreement between the preoperative 3D images and intraoperative findings, and the feeding arteries were identified and managed as anticipated. Previous studies have used angiographic evaluation to support assessment of the organ of origin in a pelvic mass [5] . Interventional radiology techniques, including digital subtraction angiography (DSA), allow detailed delineation of tumor-feeding vessels; however, they are invasive and less suited to intuitive 3D preoperative anatomical assessment. Previous studies have shown that multislice CT angiography can delineate feeding arteries with good correlation to surgical and pathological findings and may be more useful than conventional CT for evaluating tumor vascular supply [6] , [7] . Although contrast-enhanced CT does not replace DSA, it provides a less invasive means of assessing major feeding vessels and supporting preoperative estimation of the organ of origin. In combination with 3D reconstruction, it may also improve preoperative simulation and individualized surgical planning. Several reports have described retroperitoneal schwannomas in women that were preoperatively misdiagnosed as uterine leiomyomas or broad ligament fibroids [8] , [9] , [10] , [11] . These reports emphasize the difficulty of preoperative organ-of-origin assessment and the potential risks of bleeding and nerve injury due to the proximity of these tumors to major pelvic vessels and nerves. Therefore, preoperative evaluation of vascular supply and 3D anatomical relationships may contribute not only to estimation of tumor origin but also to safer surgical planning. In this case, preoperative biopsy was not performed because surgical resection was planned owing to tumor-related mass effect. Although biopsy is important for histological diagnosis, it does not always allow definitive exclusion of retroperitoneal tumors. Therefore, even when biopsy is performed, 3D CT-based vascular evaluation may still provide additional value for surgical planning. Despite substantial intraoperative blood loss related primarily to venous injury, preoperative assessment of the arterial anatomy was useful for ureteral dissection and systematic vascular control. However, this discrepancy also highlights an important limitation of arterial-phase-focused imaging, as venous anatomy and bleeding risk could not be adequately predicted. Future protocols incorporating venous-phase vascular reconstruction may further improve preoperative risk assessment. This case has several limitations. First, the indication for total hysterectomy with bilateral salpingo-oophorectomy may be debatable in retrospect. However, given the patient's perimenopausal status and the anticipated difficulty in securing an adequate operative field, this approach was considered appropriate from a surgical safety perspective. Second, although arterial supply was accurately assessed preoperatively, venous anatomy was not sufficiently evaluated, which contributed to unexpected intraoperative bleeding.

This article was not commissioned and was peer reviewed.

During the preparation of this work, the authors used ChatGPT (OpenAI) to assist with English language editing and improvement of readability. After using this tool, the authors reviewed and edited the output as needed and take full responsibility for the content of the published article.

Daiki Idegami contributed to patient care, conception of the case report, acquiring and interpreting the data, drafting the manuscript, undertaking the literature review and revising the article critically for important intellectual content. Yuji Tanaka contributed to patient care, conception of the case report, interpreting the data, drafting the manuscript and revising the article critically for important intellectual content. Hiroyuki Yamanaka contributed to patient care, acquiring and interpreting the data and revising the article critically for important intellectual content. Yutaka Yoneoka contributed to patient care, acquiring and interpreting the data and revising the article critically for important intellectual content. Akimasa Takahashi contributed to patient care, interpreting the data and revising the article critically for important intellectual content. Akie Takebayashi contributed to patient care, interpreting the data and revising the article critically for important intellectual content. Tsukuru Amano contributed to patient care, interpreting the data and revising the article critically for important intellectual content. Kenji Isogawa contributed to patient care, interpreting the data and revising the article critically for important intellectual content. Suzuko Moritani contributed to patient care, interpreting the data and revising the article critically for important intellectual content. Shunichiro Tsuji contributed to patient care, interpreting the data and revising the article critically for important intellectual content. All authors approved the final submitted manuscript.

In women presenting with a pelvic mass adjacent to the uterus and with both ovaries evaluated as normal, uterine tumors such as leiomyomas are usually considered first, and management is often undertaken by gynecologists. However, retroperitoneal tumors arising near the uterus should also be included in the differential diagnosis [1] . Magnetic resonance imaging (MRI) plays a central role in the preoperative evaluation of pelvic tumors by providing detailed information regarding tumor morphology and anatomical relationships. However, when a tumor closely abuts the uterus and continuity between the tumor and uterus is unclear, determining the organ of origin based on MRI alone may be difficult [2] . In such cases, evaluation of the tumor vascular supply may provide additional diagnostic information and facilitate surgical planning. Recent advances in contrast-enhanced computed tomography (CT) with 3D reconstruction have enabled noninvasive evaluation of tumor vascular anatomy and spatial relationships [3] , [4] . However, its application to estimating the organ of origin in gynecologic tumors has been infrequently reported. This report describes a case of a pelvic mass adjacent to the uterus in which evaluation of feeding vessels using contrast-enhanced CT with 3D reconstruction using SYNAPSE VINCENT (Fujifilm Medical Co., Ltd., Tokyo, Japan), integrated with surgical planning and intraoperative guidance, enabled preoperative estimation of a retroperitoneal origin and facilitated individualized surgical planning.

The authors declare that they have no competing interest regarding the publication of this case report.