Rapidly growing anterior mediastinal teratoma in a young adult female: successful resection via robotic-assisted thoracoscopic surgery

Abstract

Introduction:

Mediastinal teratomas are rare, typically benign germ cell tumors that are often discovered incidentally due to their slow growth and asymptomatic nature.

Presentation of the Case:

We present this unusual case of a 22-year-old woman who presented with retrosternal chest discomfort, and was incidentally found to have a large anterior mediastinal mass measuring 8 × 8 × 5 cm on computed tomography (CT) scan. Imaging characteristics – including fat and calcification – were consistent with a mature cystic teratoma. Notably, a CT scan performed 4 years earlier was completely normal, suggesting unusually rapid tumor growth. The patient underwent robotic-assisted thoracoscopic surgery (RATS) for resection of the mass. Intraoperatively, the lesion was found to be cystic and adherent to the pericardium and closely associated with the right phrenic nerve, without clear evidence of invasion. The procedure was completed successfully, with an uneventful postoperative recovery. Histopathologic analysis confirmed a mature teratoma without malignant features.

Discussion:

Although mediastinal teratomas are classically indolent, this rare case illustrates that they may occasionally demonstrate rapid growth and present unexpectedly. Timely imaging and intervention are crucial in such scenarios. The anatomical complexity of the mediastinum presents surgical challenges, especially in large masses.

Conclusion:

This case highlights the potential for rapid growth in mediastinal teratomas and supports the feasibility and safety of RATS as a minimally invasive approach. This technique enables excellent exposure and precise dissection in anatomically complex regions, with favorable patient outcomes.

Introduction

Teratomas are rare germ cell tumors composed of tissues originating from all three embryonic germ layers: ectoderm, mesoderm, and endoderm. These tumors can arise in various anatomical sites, most commonly in the gonads, but also in extragonadal regions such as the anterior mediastinum, retroperitoneum, and sacrococcygeal area^[1,2^]. Mediastinal teratomas represent the most frequent primary germ cell tumors of the mediastinum, particularly in young adults. While the majority are histologically mature and benign, with reported growth rates of only a few centimeters per year, a subset can undergo malignant transformation, underscoring the need for early recognition and definitive management^[1–4^].

The clinical presentation of mediastinal teratomas is often nonspecific^[2,4^]. Many are discovered incidentally on imaging, but larger lesions may present with symptoms such as chest pain, dyspnea, cough, or signs of compression of intrathoracic structures, including the heart and great vessels^[5,6^]. Imaging plays a critical role in diagnosis and surgical planning, with computed tomography (CT) and magnetic resonance imaging (MRI) offering key insights into tumor composition – particularly the presence of fat, fluid, and calcification, which are characteristic of mature teratomas^[4^].

Surgical resection remains the cornerstone of treatment. The technical complexity of surgery is influenced by the tumor’s size, its proximity or adherence to vital structures, and the risk of complications such as rupture or bleeding. Minimally invasive techniques, including video-assisted thoracoscopic surgery and robotic-assisted thoracoscopic surgery (RATS), have increasingly been adopted for resection, with promising outcomes in select cases^[7^]. A multidisciplinary approach, involving thoracic surgeons, radiologists, anesthesiologists, oncologists, and pathologists, is essential for ensuring safe and effective management^[8^].

This unusual case highlights a rare presentation of a large, rapidly growing mature mediastinal teratoma in a young female patient, with atypical symptomatology and significant mass effect. It also highlights the benefit of robotic-assisted surgery for a mediastinal tumor of this size. We describe the diagnostic process, surgical management, and postoperative outcomes, and review relevant literature on similar cases. This case report has been reported in line with the SCARE checklist^[9^].

Presentation of case

A 22-year-old healthy woman presented for evaluation of a mediastinal mass, initially identified following complaints of right shoulder pain and retrosternal chest discomfort, particularly during deep inspiration and at night. A chest X-ray performed in the emergency department revealed a well-defined mass in the right hemithorax at the level of the hilar structures (Fig. 1).

Figure 1.

(A) Posteroanterior (PA) chest radiograph and (B) lateral chest radiograph of a 22-year-old female patient obtained in the emergency department, demonstrating a well-circumscribed mediastinal mass consistent with a teratoma.

A contrast-enhanced chest CT was then performed, revealing a well-demarcated, heterogeneous mass in the anterior mediastinum, measuring 76 × 80 mm, with internal coarse calcifications and fat-density areas, highly suggestive of a mature teratoma. The mass compressed the superior vena cava and displaced the heart toward the left. Review of a CT scan (performed for unrelated back pain 4 years earlier) showed no evidence of a mediastinal lesion, also mentioned in the original radiological report, indicating rapid growth over this interval (Fig. 2).

Figure 2.

(A) Coronal CT scan from 2021 performed for back pain, showing normal mediastinal anatomy with no evidence of a teratoma. (B) Sagittal CT scan from 2025 demonstrating a well-defined anterior mediastinal mass with fat-density components and coarse calcifications, consistent with a mature teratoma.

Upon presentation to the emergency department, the patient was hemodynamically stable: blood pressure 123/84 mmHg, heart rate 80 bpm, temperature 36.7°C, oxygen saturation 97% on room air. Physical examination revealed no abnormal findings aside from slightly reduced air entry in the right parasternal area.

A repeat contrast-enhanced chest computed tomography angiography (CTA) was performed 6 weeks later, confirming the size, morphology, and internal components of the mediastinal mass. The CTA clearly demonstrated significant compression of the right heart and great vessels, including anterior displacement of the right atrium and narrowing of the superior vena cava. No pericardial or pleural effusion was identified. However, despite the enhanced vascular detail provided by CTA, definitive assessment of pericardial involvement remained inconclusive. Pulmonary function testing revealed a mildly reduced forced expiratory volume in one second (FEV₁) with a normal diffusing capacity, suggesting the absence of significant obstructive or restrictive lung disease. Routine laboratory tests, including complete blood count, comprehensive metabolic panel, and tumor markers (AFP, β-HCG, CEA, CA-125, CA 19-9), were all within normal limits. A gynecologic consultation and pelvic ultrasound ruled out any similar pathology involving the ovaries or pelvic organs.

HIGHLIGHTS

• Exceptionally rapid growth of a large anterior mediastinal teratoma over 4 years in a young adult female, despite previous normal imaging.

• Successful en bloc resection of a complex mediastinal mass closely adherent to vital structures using robotic-assisted thoracoscopic surgery (RATS).

• Preservation of the right phrenic nerve and avoidance of pericardial resection in a high-risk anatomical setting.

• Demonstrates the feasibility and safety of RATS for large mediastinal tumors in experienced hands.

• Adds to the limited literature on accelerated growth of mature mediastinal teratomas and minimally invasive management strategies.

Therapeutic intervention

The patient underwent RATS using the da Vinci Xi system for resection of the anterior mediastinal mass. The resection was carried out under general anesthesia in a supine position, utilizing three 8-mm robotic ports and an additional 12-mm assistant port. Of note, one 8-mm port and the assistant port were 4 cm apart, located both in the inferior right breast fold. Intraoperatively, the tumor was noted to be well-encapsulated but heavily adhered to surrounding structures such as superior vena cava, right lung, and pericardium. Located in close proximity to the right phrenic nerve, the mass was carefully resected en bloc along with a small wedge of the right upper lobe. Dissection was performed using a combination of sharp and blunt techniques while maintaining continuous visualization of the phrenic nerve (Supplemental Digital Content Video, available at: http://links.lww.com/IJSCR/A21). Adhesions to the superior vena cava were carefully separated with precise sharp dissection, and the tumor was completely resected (Supplemental Digital Content Figure 1A, available at: http://links.lww.com/JS9/H11). The mass was firm and was placed in a reinforced endoscopic bag. It was then removed through incision that bridged the two previous incisions located on the breast fold. A right chest tube was inserted intraoperatively as part of the standard postoperative drainage protocol.

The surgical procedure and the postoperative recovery were uneventful. The chest tube was removed on postoperative day 1, and the patient was discharged home. Histopathologic examination confirmed an 8 × 8 × 5 cm mature cystic teratoma composed of well-differentiated tissue elements from all three germ layers, with no evidence of malignant transformation. Fusion testing was not available for this case.

Follow-up and outcomes

At the 2-week postoperative follow-up visit, the surgical wounds were clean and demonstrated appropriate healing (Supplemental Digital Content Figure 1B, available at: http://links.lww.com/JS9/H11). A chest X-ray showed no pathological findings. The patient reported minimal postoperative pain, which was well controlled with oral analgesics.

Discussion

This case report presents a rare but instructive instance of a mature anterior mediastinal teratoma in a young adult female, with three notable aspects: rapid tumor growth, diagnostic uncertainty regarding pericardial involvement, and the use of RATS for the resection of a large mediastinal mass.

Mature teratomas are typically benign and slow-growing. Their occurrence in the breast is exceptionally rare, particularly without any ovarian lesions, as germ cells are ordinarily confined to the gonads^[8,10^]. Nevertheless, our patient demonstrated tumor progression over 4 years, from a completely normal chest CT to an 8 cm mass. This finding suggests that mature teratomas may occasionally exhibit accelerated growth, possibly in response to internal changes such as hemorrhage, fat necrosis, or cyst rupture. The clinical implications are twofold: (1) even presumed benign, mediastinal masses warrant close and continued surveillance, and (2) rapid tumor expansion even in asymptomatic individuals necessitates early surgical intervention – particularly when adjacent mediastinal structures are affected. Our findings support prior literature emphasizing the unpredictable behavior of some mature teratomas and the need for vigilant imaging follow-up^[4–6^].

Although mature teratomas are generally noninvasive tumors, they can erode into adjacent structures and lead to serious complications^[10^]. In this case, the tumor caused significant mass effect, displacing the heart and compressing the superior vena cava. Despite high-resolution imaging, including contrast-enhanced CT angiography, it was not possible to determine with certainty whether the pericardium was merely compressed or actually invaginated or involved by the tumor. This diagnostic uncertainty had critical implications for surgical planning, particularly with regard to the potential need for conversion to open surgery through mid-sternotomy or need for pericardial resection. Intraoperative findings did not reveal such invasion, and resection was achieved without entering the pericardial space. Still, this limitation underscores the persistent challenges of accurately assessing large mediastinal tumors preoperatively and emphasizes the need for careful surgical planning. This requires readiness to convert to open surgery and the availability of appropriate expertise and equipment. Close collaboration with cardiothoracic surgeons, anesthesiologists, and radiologists is essential, highlighting the importance of intraoperative flexibility^[11^].

Robotic platforms are increasingly used for mediastinal procedures, particularly thymectomies and resection of small lesions. However, evidence remains limited regarding their use in large (>7 cm) tumors^[12,13^]. In this instance, the robotic approach provided superior visualization, fine dissection, and enhanced dexterity, facilitating safe and complete excision despite the mass’s proximity to vital structures such as the heart and great vessels and right phrenic nerve. No intraoperative complications occurred, and the patient had a rapid, uneventful recovery. Literature supports several advantages of RATS, including reduced postoperative pain, fewer complications, shorter hospitalization, and faster return to baseline activity^[7,14,15^]. At our institution, robotic thoracic procedures are performed routinely, which has allowed the surgical team to develop substantial experience with complex mediastinal cases. With increasing proficiency, tumor size became less restrictive, and the degree of adherence to adjacent structures on imaging emerged as the main factor guiding the operative approach. Our experience contributes to the growing body of evidence suggesting that robotic platforms may be both feasible and advantageous even in technically demanding cases, provided there is sufficient surgical expertise and institutional support.

Conclusion

Anterior mediastinal teratomas should be considered in the differential diagnosis of chest pain in young adults, particularly when accompanied by compressive symptoms. Rapid growth of such lesions, even in the absence of malignant features, warrants timely surgical intervention. This case highlights the diagnostic challenges posed by potential pericardial involvement and illustrates the expanding role of robotic surgery in the management of large anterior mediastinal masses.

Ethical approval

All data for this case report were retrospectively collected from the electronic medical records of the Soroka University Medical Center (SUMC). Data extraction was performed by authorized personnel with institutional access. Ethical approval for the study was obtained from the Ethics Committee of the Soroka University Medical Center (approval number SOR-0174-25, dated 1 May 2025) prior to data collection.

Consent

All identifying patient information has been anonymized. Informed consent was waived due to complete removal of personal identifiers. 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 Editor-in-Chief of this journal on request.

Sources of funding

No external funding was received for this report.

Author contributions

M.S.: conceptualization of the case report, data collection and analysis, drafting and revision of the manuscript, preparation of figures and video. E.B.G.: assistance with data acquisition, literature review, and manuscript editing. L.R.: surgical assistance, clinical data interpretation, and manuscript revision. A.L.: surgical performance, critical input on case analysis, and review of manuscript content. A.A.: intraoperative and clinical supervision, manuscript editing, and figure preparation. Y.R.: senior surgical oversight, critical revision for important intellectual content, and final approval of the manuscript. All authors read and approved the final version of the manuscript.

Conflicts of interest disclosure

The authors declare no conflicts of interest.

Research registration unique identifying number (UIN)

Not applicable.

Provenance and peer review

This article is a standard submission and has undergone external double-blind peer review.

Data availability statement

The data used during the current study are available from the corresponding author on reasonable request.

Guarantor

Elad Bar Gil accepts full responsibility as the guarantor for the integrity of the content of this case report, confirms access to all data, and affirms control over the decision to publish.

Footnote

The authors have completed the Surgical CAse REport (SCARE) reporting checklist.

Patient perspective

Not applicable as this case report was retrospective, using de-identified data from institutional electronic records.

Declaration of generative AI and AI-assisted technologies in the writing process

During the preparation of this work, the authors used ChatGPT by OpenAI to assist in improving grammar, style, and structure. All inputs have been de-identified. The authors reviewed and edited the content and take full responsibility for the content of the publication.