Treatment of an invasive thymoma-like left innominate venous aneurysm using allogeneic pericardium with continuous horizontal mattress sutures: a case report

Introduction

Left innominate venous aneurysm is an unusual vascular disease that has only been occasionally reported, and the cause of this disease remains to be determined. It is often found as an asymptomatic anterior superior mediastinal mass, which is often misdiagnosed as thymoma but can be definitively diagnosed intraoperatively (1-3). Standard therapeutic guidelines for left innominate venous aneurysms have not yet been established, and the treatment strategies implemented are left to the discretion of the medical team. Surgery is frequently favored, but the surgical methods vary considerably. To our knowledge, this is the first reported case of using allogeneic pericardium with continuous horizontal mattress sutures to treat a left innominate vein aneurysm (LIVA). This novel approach may offer valuable insights for guiding future therapeutic strategies. We present this case in accordance with the CARE reporting checklist (available at https://jtd.amegroups.com/article/view/10.21037/jtd-2025-1189/rc).

Case presentation

A 55-year-old male was incidentally found to have an anterior mediastinal mass. The chief complaints did not include chest pain, dyspnea, or symptoms of myasthenia gravis. The patient was in good health. No abnormally positive signs were found in the physical examination. The computed tomography (CT) scan showed that the mass was located in the anterior mediastinal region and had a size of approximately 3.5 cm × 3.5 cm × 3.0 cm. Invasive thymoma was suspected. Contrast-enhanced CT also displayed an anterior mediastinal soft tissue density with vascular enhancement that included the tortuous left innominate vein (Figure 1). A median sternotomy was performed, the left innominate vein was visually dilated, and a cystic aneurysm was identified on the surface of the blood vessel with a size of approximately 3.0 cm × 3.5 cm. The cystic vessel wall was thin and without thrombosis (Figure 2A). Lacking a pedicle, the aneurysm was sutured with 4-0 Prolene sutures, and allogeneic pericardium was applied using continuous horizontal mattress sutures to close the aneurysm and reinforce the venous wall (Figure 2B). The patient had an uneventful postoperative course and was discharged 7 days after surgery (Figure 3). Last followed up in March 2022, 1 year post-surgery, with no recurrence. No anticoagulation was needed due to no intraoperative thrombosis and normal flow on Doppler ultrasound. The next follow-up is scheduled for March 2026, at the 5-year postoperative mark.

Figure 1 CT images of the patient. Contrast-enhanced CT displayed a large saccular aneurysm in the left brachiocephalic vein during the different phase (yellow arrows). Scale bar =5 cm. CT, computed tomography; L, left; R, right.

Figure 2 Intraoperative findings. (A) After median sternotomy, the left innominate venous aneurysm was fully exposed (yellow arrow). (B) The aneurysm was sutured closed with allogeneic pericardium (yellow arrow).

Figure 3 Diagnostic and therapeutic timeline. Key milestones from initial detection to discharge from hospital are shown. CT, computed tomography.

All procedures in this study were performed in accordance with the ethical standards of the institutional and/or national research committee(s) and with the Declaration of Helsinki and its subsequent amendments. Written informed consent was obtained from the patient for publication of this case report and accompanying images. A copy of the written consent is available for review by the editorial office of this journal.

International multidisciplinary team (iMDT) discussion

Discussion among physicians from the Department of Cardiothoracic Surgery, Benxi Central Hospital

Innominate venous aneurysm is exceedingly rare. According to the PubMed database, no more than 30 cases have been reported to date. Innominate venous aneurysms are predominantly on the left and can be isolated, saccular-shaped, or combined with aneurysms of the superior vena cava. Most patients are often asymptomatic, and the disease is often misdiagnosed as invasive thymoma on preoperative CT scans. Contrast-enhanced three-dimensional (3D) CT angiography (CTA) or magnetic resonance venography (MRV), with venous-phase imaging, is critical to differentiate aneurysms from thymomas.

The etiology of innominate venous aneurysms remains undetermined. The known causes include congenital malformations, trauma, infection, iatrogenic injury, degeneration, and tumors (4,5). Venous aneurysms may cause severe complications such as aneurysm rupture and thrombosis, which may lead to pulmonary embolism (PE). Therefore, these aneurysms should be treated quickly; however, therapeutic guidelines have not been established. The majority of reported patients underwent surgeries, such as aneurysmectomy repaired with or without autologous pericardium (2,6), bypass grafting, and reconstruction of the innominate vein (1,7), which have achieved good results, with no postoperative recurrences being reported. There have also been attempts to use endovascular stenting, but this may be controversial due to ethical issues related to the design and use of medical devices (8). Minimally invasive surgical methods have also been reported (3,9,10), and autologous grafts have been implemented for aneurysms but not for venous aneurysms (11,12).

In our case, the patient was asymptomatic, suggesting the cause of the aneurysm to be congenital malformation. Contrast-enhanced CT is needed for diagnosis, with venous-phase images being paramount; these images could reduce the misdiagnosis rate of invasive thymoma and video-assisted thoracoscopic surgery (VATS), which may lead to a bleeding risk (13). In our case, median sternotomy was performed, and the aneurysm did not have a pedicle but appeared to be ruptured and was treated by the procedure described above. This procedure could not only eliminate aneurysms but also strengthen the venous wall to avoid recurrence of aneurysm. The suture approach, which was rapid and straightforward, could prevent massive bleeding and the use of cardiopulmonary bypass (CPB). Anticoagulant therapy was not offered as there was no intraoperative thrombosis with normal flow on Doppler ultrasound. Thus far, no recurrence has occurred.

This study has several limitations. As a single-case report, its findings are descriptive in nature and lack broader applicability. The clinical benefit of the surgical approach remains to be confirmed in larger patient populations, particularly those with more complex disease or comorbid conditions. In the absence of comparative data, the relative advantages over alternative interventions remain unclear. The presumed congenital origin of the aneurysm was not definitively established, as further etiological evaluation was not performed. Additionally, the limited follow-up duration precludes assessment of long-term durability and potential late complications.

Several issues on the treatment of these patients were further discussed as follows

Diagnostic challenges: given the rarity of LIVAs and their frequent misdiagnosis as invasive thymoma, what additional imaging modalities or diagnostic criteria could be prioritized to improve preoperative accuracy? How might an international team collaborate to standardize diagnostic protocols?

Mohamed Shanshal: The rarity of LIVAs and their frequent misdiagnosis as invasive thymoma highlight the need for advanced imaging. Contrast-enhanced CTA with 3D reconstruction should interpretation of vascular anatomy, distinguishing aneurysms from solid masses. MRV or four-dimensional (4D) flow magnetic resonance imaging (MRI) can further assess flow dynamics, reducing misdiagnosis risk. For example, venous-phase imaging, as used in this case, was critical for identifying the aneurysm. An international team could collaborate via the iMDT platform to standardize diagnostic protocols, integrating CTA/MRV criteria and multidisciplinary input (radiology, vascular surgery, thoracic oncology). A global registry for venous aneurysms could aggregate imaging data to refine diagnostic algorithms.

Apostolos C. Agrafiotis: A contrast-enhanced CT scan should be a part of the preoperative workup.

Matthias Lang: A retrosternal duplex ultrasonography will quickly confirm diagnosis. In general, the standardized diagnostic protocols for chest and neck CT and MRI with arterial and venous contrasting should apply. Vascular Doppler and duplex ultrasound are recommended to quantify blood flow.

Shinkichi Takamori: LIVAs are rare and often misdiagnosed as invasive thymomas. To improve preoperative diagnostic accuracy, a multi-modality imaging approach is essential, using contrast-enhanced CT, MRI, Doppler ultrasound, and CT venography/intravascular ultrasound (IVUS). Key diagnostic criteria include homogeneous enhancement in the venous phase; biopsy is contraindicated. International collaboration is needed to standardize diagnostic protocols, including case registries, consensus-based diagnostic algorithms, and published guidelines.

Yosuke Yamada: To be honest, I did not recognize that LIVAs are a differential diagnosis of anterior mediastinal mass. It was fortunate that the patient did not receive a needle biopsy. I am not familiar with imaging modalities, but patients with mediastinal masses sometimes receive fluorodeoxyglucose (FDG)-positron emission tomography (PET) in Japan. This may also be useful for distinguishing thymoma and aneurysm. Since available modalities vary from country to country, collaboration across nations will undoubtedly aid in establishing an international standard that consider the differences.

I wonder whether non-thymomatous lesions, such as germ cell tumors and thymic cysts, could also be considered in the differential diagnosis of an aneurysm. If that is the case, please include them as differential diagnoses. However, if you have a rationale that thymoma is the only differential diagnosis, feel free to disregard my suggestions.

Surgical strategy: the case highlights a novel technique using allogeneic pericardium with continuous horizontal mattress sutures, avoiding vascular grafts or CPB. How might this approach be optimized or adapted for high-risk patients (e.g., those with comorbidities or larger aneurysms)? Are there minimally invasive alternatives (e.g., thoracoscopy) that could be considered?

Mohamed Shanshal: The novel technique using allogeneic pericardium with continuous horizontal mattress sutures is a significant advancement, avoiding vascular grafts and CPB. For high-risk patients (e.g., those with comorbidities or larger aneurysms), optimization could involve preoperative risk assessment using tools like the Charlson Comorbidity Index and tailoring anesthesia to minimize cardiopulmonary stress. For larger aneurysms (>5 cm), synthetic patches (e.g., Dacron) may enhance durability if allogeneic tissue is insufficient. VATS could be considered for smaller aneurysms, though limited by visualization challenges in the mediastinum. A feasibility study comparing VATS to open sternotomy is warranted. I suggest a brief discussion on patient selection for this technique and the potential limitations of VATS.

Apostolos C. Agrafiotis: No data is supporting the use of minimally invasive techniques due to the rarity of the disease. For small lesions, a minimally invasive technique may be a valid alternative.

Matthias Lang: Minimal invasive alternatives and transvascular stenting techniques could be considered depending on expertise.

Shinkichi Takamori: The allogeneic pericardium patch technique offers a less invasive option for repairing LIVAs in high-risk patients, avoiding CPB. This approach includes customized patch sizing and careful suturing. While minimally invasive alternatives like VATS and robotic surgery show promise, current evidence is largely based on case reports. These approaches should be considered with caution until more robust evidence emerges. Success depends on perioperative optimization and appropriate case selection, with readiness to convert to open surgery if needed.

Yosuke Yamada: I don’t have any knowledge/experience to answer this question.

Postoperative management: the patient required no anticoagulant therapy postoperatively, contrary to some reported cases. What factors should guide the decision to use anticoagulation after venous aneurysm repair? How would an MDT balance thrombosis prevention against bleeding risks in such scenarios?

Mohamed Shanshal: The absence of anticoagulant therapy in this case is notable, given reported cases using anticoagulation. The decision should be guided by aneurysm size, residual flow stasis (assessed via Doppler ultrasound), and patient-specific risks (e.g., history of thromboembolism or comorbidities like atrial fibrillation). An MDT should balance thrombosis prevention against bleeding risk using tools like the Caprini score for thrombosis and HAS-BLED for bleeding. In this case, the lack of thrombosis intraoperatively likely justified omitting anticoagulation.

Apostolos C. Agrafiotis: There is no data to support either strategy; in the absence of vascular graft implantation, postoperative anticoagulation could be omitted.

Matthias Lang: A thorough history taking including bleeding and thromboembolism as well as family history is necessary to decide. In unclear cases, I recommend the consultation of a haemostaeologist.

Shinkichi Takamori: Thrombotic risk factors, including preoperative or postoperative thrombus, large aneurysms, and a history of PE/deep vein thrombosis (DVT), often warrant anticoagulation. Bleeding risks such as advanced age, liver impairment, and complex surgery must be weighed carefully. Regarding MDT approach, validated tools (e.g., Caprini score for thrombosis, HAS-BLED for bleeding) to quantify risks are useful. It is important to prioritize anticoagulation in high-thrombotic-risk patients (e.g., residual thrombus, prior PE/DVT).

Yosuke Yamada: I don’t have any knowledge/experience to answer this question.

Etiology and prevention: with the etiology of innominate vein aneurysms remaining unclear (congenital vs. acquired), what long-term monitoring or preventive strategies would an iMDT recommend for asymptomatic patients with incidental findings? Are there biomarkers or genetic studies that could clarify pathogenesis?

Mohamed Shanshal: The unclear etiology (congenital vs. acquired) complicates prevention strategies. Annual CTA or MRV is recommended for asymptomatic aneurysms, with genetic testing [e.g., COL3A1 for Ehlers-Danlos syndrome (EDS)] to explore congenital causes. Biomarkers like D-dimer or CRP may suggest acquired etiologies. International registries could standardize monitoring protocols.

Apostolos C. Agrafiotis: A contrast-enhanced CT scan performed annually may be sufficient. In case of aneurysm enlargement, more frequent imaging should be performed. There are no biomarkers that could contribute to the diagnosis.

To the best of my knowledge, there are no reliable genetic or blood-borne biomarkers.

Shinkichi Takamori: The etiology of LIVA is complex, involving congenital factors [e.g., developmental anomalies, neurofibromatosis type 1 (NF1)] and acquired factors (e.g., chronic venous hypertension, trauma). For asymptomatic patients, imaging follow-up (e.g., CT/MRI, venography, Doppler ultrasound) is recommended based on risk stratification; I personally suggest annual or semi-annual intervals depending on risk. Thromboprophylaxis may be needed for thrombus-containing aneurysms, and activity modifications should be advised. Biomarker research (e.g., MMP-2/TIMP-4 imbalance, granzyme K) and genetic studies (e.g., NF1, COL3A1/COL4A1) may enhance risk prediction. International collaboration, including a global registry and AI-based risk prediction, is needed to refine management strategies.

Yosuke Yamada: I recognize that genetics plays a role in the development of venous aneurysms. For example, aneurysmal lesions are commonly observed in EDS. You may check whether the documented cases of LIVAs have a genetic disease, family history, and so on. If you find any relevant reports, you may reference them in this manuscript. Even if you cannot find such reports, assessing factors known to be associated with more common venous aneurysms might help explore the etiology of the aneurysm in these patients. I do not know of biomarkers for venous aneurysms.

Global perspectives on rare cases: how can international collaboration (e.g., shared registries or telemedicine consults) improve outcomes for rare vascular anomalies like this? What role might “iMDT” play in refining guidelines for such understudied conditions?

Mohamed Shanshal: International collaboration via shared registries (e.g., hosted by iMDT or the Society for Thoracic Surgery) can pool data on rare vascular anomalies, improving diagnostic and therapeutic outcomes. Telemedicine consults enable real-time MDT discussions, integrating expertise from radiologists, surgeons, and oncologists globally. The iMDT platform could lead guideline development by synthesizing case reports, imaging data, and surgical outcomes into consensus statements. I recommend that the manuscript emphasize iMDT’s role in creating open-access data repositories to accelerate research on understudied conditions like innominate vein aneurysms.

Apostolos C. Agrafiotis: National and international databases and data sharing could contribute to the better understanding of the pathogenesis of this rare entity.

Matthias Lang: Shared registries or telemedicine consults would be strong tools for rare diseases. But different international legal issues on data protection often hinders such an initiative.

Shinkichi Takamori: International registries like VASCA and SPIDER are effective for pooling data on LIVA, given its rarity (~40 reported cases globally). Telemedicine platforms facilitate cross-border expert consultations, enhancing diagnostic accuracy and surgical outcomes. iMDT approaches are particularly effective and valuable because they bring together diverse specialists, including surgeons, radiologists, internists, geneticists, and hematologists, to collectively interpret fragmented case reports. This collaborative process contributes to the development of evidence-based guidelines. As telemedicine and AI evolve, iMDTs will play a critical role in refining global guidelines for rare anomalies.

Yosuke Yamada: I believe that international collaboration is essential for collecting a sufficient number of cases, sharing information, and establishing new, effective strategies for rare diseases. It may also reveal differences among countries (incidence, age, gender of the disease, etc.), which could indicate certain etiologic factors of the disease.

Conclusions

Evaluation of mediastinal masses should include contrast-enhanced CT or MRI, especially if a left innominate venous aneurysm is suspected preoperatively. Median sternotomy is recommended, and the surgeon should dissect carefully to avoid injury to the aneurysm. Our management strategy in this case was safe, convenient, and effective. Given the rarity of left innominate venous aneurysm, international collaboration would be valuable to establish standardized guidelines for managing this uncommon condition.

Acknowledgments

None.

Footnote

Reporting Checklist: The authors have completed the CARE reporting checklist. Available at https://jtd.amegroups.com/article/view/10.21037/jtd-2025-1189/rc

Peer Review File: Available at https://jtd.amegroups.com/article/view/10.21037/jtd-2025-1189/prf

Funding: This publication was supported by the National Natural Science Foundation of China (to F.X.) (No. 81701570).

Conflicts of Interest: All authors have completed the ICMJE uniform disclosure form (available at https://jtd.amegroups.com/article/view/10.21037/jtd-2025-1189/coif). The authors have no conflicts of interest to declare.

Ethical Statement: The authors are accountable for all aspects of the work in ensuring that questions related to the accuracy or integrity of any part of the work are appropriately investigated and resolved. All procedures in this study were performed in accordance with the ethical standards of the institutional and/or national research committee(s) and with the Declaration of Helsinki and its subsequent amendments. Written informed consent was obtained from the patient for publication of this case report and accompanying images. A copy of the written consent is available for review by the editorial office of this journal.

Open Access Statement: This is an Open Access article distributed in accordance with the Creative Commons Attribution-NonCommercial-NoDerivs 4.0 International License (CC BY-NC-ND 4.0), which permits the non-commercial replication and distribution of the article with the strict proviso that no changes or edits are made and the original work is properly cited (including links to both the formal publication through the relevant DOI and the license). See: https://creativecommons.org/licenses/by-nc-nd/4.0/.

References

1. Huang W, Jiang GN. A rare case of left innominate vein aneurysm mimicking thymoma. Interact Cardiovasc Thorac Surg 2017;25:669-70. [Crossref] [PubMed]
2. Shen J, Wang W, Li F, et al. Surgical treatment for rare isolated left innominate vein aneurysms. Interact Cardiovasc Thorac Surg 2019;28:989-91. [Crossref] [PubMed]
3. Ueno H, Yazawa M, Tsubouchi H, et al. Left brachiocephalic vein aneurysm: a case report. Surg Case Rep 2021;7:66. [Crossref] [PubMed]
4. Mikroulis D, Vretzakis G, Eleftheriadis S, et al. Long-term antiplatelet treatment for innominate vein aneurysm. Vasa 2010;39:262-4. [Crossref] [PubMed]
5. Akiba T, Morikawa T, Hirayama S, et al. Thymic haemangioma presenting with a left innominate vein aneurysm: insight into the aetiology. Interact Cardiovasc Thorac Surg 2012;15:925-7. [Crossref] [PubMed]
6. Galvaing G, Gaudin M, Medous MT, et al. Left Brachiocephalic Venous Aneurysm: A Rare Clinical Finding. Ann Vasc Surg 2018;48:253.e5-6. [Crossref] [PubMed]
7. Mehra R, Swain P, Aggarwal R, et al. Complex aortic-arch pseudoaneurysm with aorto-innominate vein fistula in a case of traumatic chest injury. BMJ Case Rep 2024;17:e260184. [Crossref] [PubMed]
8. Cai G, Hua Z, Xu P, et al. Endovascular treatment for left innominate vein aneurysm: Case report and literature review. J Interv Med 2019;2:35-7. [Crossref] [PubMed]
9. Hu Y, Ren S, Zeng C, et al. Case Report: Surgical Therapy for Left Innominate Vein Aneurysm Under Thoracoscopy. Front Surg 2021;8:741840. [Crossref] [PubMed]
10. Kim SP, Son J. Simultaneous lateral and subxiphoid access methods for safe and accurate resection of a superior vena cava aneurysm: A case report. World J Clin Cases 2023;11:7635-9. [Crossref] [PubMed]
11. Inam H, Ahad A, Sundardas R, et al. Autologous vein graft repair of mycotic innominate artery aneurysm: A case report. Int J Surg Case Rep 2023;103:107902. [Crossref] [PubMed]
12. Mulawardi , Jancung , Faruk M, et al. A rare case of femoral artery saccular aneurysm caused by tuberculosis in a male patient: A case report and review of literature. Int J Surg Case Rep 2023;106:108143. [Crossref] [PubMed]
13. Li JH, Liu YZ, Zhang H. Isolated left innominate vein aneurysms: two cases reports and literature review. International Journal of Medical Radiology 2024;47:236-8, 246.

(English Language Editor: J. Gray)