A case of giant thymolipoma: case report

Introduction

Thymolipoma is a rare benign tumor of the anterior mediastinum, composed of mature adipose tissue and benign thymic components (1,2). Thymolipoma accounts for approximately 2–9% of all thymic neoplasms, and its association with myasthenia gravis (MG) is notably low, occurring in only 2–9% of cases, in stark contrast to thymoma where the association is approximately 50% (1,2).This lesion typically grows slowly and often causes compression symptoms such as cough, dyspnea, or chest tightness only after reaching considerable size (3). Computed tomography (CT) is highly suggestive for diagnosis, typically revealing a well-defined mass with predominantly fatty density that conforms to the contours of the adjacent heart and diaphragm (1,4). Complete surgical resection constitutes the curative treatment (3).

Surgical management of mediastinal tumors has significantly shifted toward minimally invasive techniques. However, a notable gap remains in the literature regarding the application of ultra-minimally invasive approaches, such as dual-port thoracoscopy, for excising large thymolipoma. Conventional wisdom holds that such massive tumors (typically defined as having a maximum diameter >15 cm) are only suitable for open thoracotomy or median sternotomy, primarily due to technical challenges in exposure, manipulation, and safe specimen retrieval (5). Although recent sporadic reports confirm the feasibility of surgical resection for large thymolipoma (6-8), detailed descriptions of pure dual-port thoracoscopic procedures for lesions exceeding 15–20 cm remain extremely rare.

This report details the successful complete resection of a 19-cm giant thymolipoma in a 67-year-old male patient using pure dual-port thoracoscopic technique. This report aims to: (I) detail the technical essentials of dual-port thoracoscopic surgery for large benign tumors, including strategies for managing prominent vascular pedicles; (II) explore the preoperative diagnostic pathway supporting direct resection without biopsy; (III) elucidate the expanding therapeutic value of advanced minimally invasive techniques in large thymolipoma management. We present this article in accordance with the CARE reporting checklist (available at https://acr.amegroups.com/article/view/10.21037/acr-2025-299/rc).

Case presentation

A 67-year-old male patient with no significant past medical history presented with a 3-month history of progressively worsening dry cough and exertional dyspnea. He denied any symptoms suggestive of MG, such as ptosis, diplopia, or muscle weakness, and reported no chest pain or fever. Physical examination revealed markedly diminished breath sounds over the left hemithorax.

Routine laboratory tests (including complete blood count and standard biochemical parameters) were within normal limits. Pulmonary function testing demonstrated moderate restrictive ventilatory impairment. Anteroposterior chest radiographs revealed near-complete opacification of the left hemithorax with contralateral mediastinal shift. Subsequent contrast-enhanced chest CT identified a large, well-defined lesion occupying the anterior mediastinum and extending into the left pleural cavity. The tumor measured 19 cm in craniocaudal diameter, 13 cm in transverse diameter, and 4 cm in anteroposterior diameter. It exhibited uniform fatty density with multiple thin, enhancing septa and well-defined traversing vessels visible internally (Figure 1). The mass was soft and compliant, deforming with cardiac and diaphragmatic movements. Imaging revealed no evidence of infiltration, pericardial effusion, or associated lymphadenopathy. These imaging features were considered typical diagnostic characteristics of a large thymolipoma.

Figure 1 Preoperative chest CT scan. Transverse (A,B) and coronal (C,D) views. Imaging reveals a large, well-defined mass in the anterior mediastinum, predominantly fatty in density (indicated by arrows). Internal soft tissue septa and the tumor’s compliant morphology are visible, demonstrating deformability with cardiac and diaphragmatic movement without evidence of invasion.

Following multidisciplinary thoracic tumor consultation, the imaging findings were considered highly consistent with the typical radiological characteristics of a benign thymolipoma. Given the patient’s significant compression symptoms and high diagnostic certainty on CT, surgical resection was recommended.

The patient underwent general anesthesia with single-lung ventilation in the right lateral decubitus position. A pure two-port thoracoscopic approach was employed. A 1.5-cm incision was made at the left mid-axillary line in the 7th intercostal space as the 30° thoracoscope observation port. A 5-cm incision was made at the left anterior axillary line in the 4th intercostal space as the primary working port, protected by a port protector.

Initial thoracoscopic exploration revealed a large, well-encapsulated, firm, pale yellow tumor within the left hemithorax (Figure 2). The tumor exhibited mild fibrous adhesions to the mediastinal pleura, diaphragm, and pericardium, which were dissected using electrocautery hooks. The left phrenic nerve was identified along the pericardial surface and meticulously preserved throughout the procedure. Systematic dissection was then performed using an ultrasonic scalpel along the clear interface between the tumor capsule and surrounding tissues, with particular attention to identifying and dissecting the thymic horns superiorly to ensure complete excision. During dissection of the superior and medial margins, a large vascular pedicle originating from an intrathoracic/mediastinal vascular branch and closely adjacent to the ascending aorta was identified. This vessel was meticulously dissected, then ligated with non-absorbable sutures in a double-loop configuration and transected.

Figure 2 Macroscopic specimen of the resected tumor: measuring 19 cm × 13 cm × 4 cm. The capsule was intact and smooth. Serial sectioning revealed a uniformly lobulated architecture. The cut surface appeared yellow and lobulated, with soft adipose tissue interspersed with firmer thymic components.

Following complete mobilization, the tumor was found to be attached solely by the subthymic ligament, which was then transected. The specimen was entirely extracted via the anterior surgical approach. To prevent capsular rupture, the 5-cm working incision was extended to approximately 10 cm, enabling complete resection of the 19-cm tumor without the need for segmental dissection. Intraoperative hemostasis was confirmed. A single 28-Fr chest tube was inserted through the observation port. Total operative time was 210 min with an estimated blood loss of 50 mL. No conversion to open thoracotomy was required throughout the procedure.

The excised specimen measured 19 cm × 13 cm × 4 cm. Serial sections revealed a uniformly lobulated yellow fatty cut surface. Pathological examination confirmed a thymolipoma. Microscopically, mature adipocytes were interspersed with islands of benign thymic tissue containing lymphocytes and numerous Hassall’s corpuscles. No cytological atypia or malignant features were observed (Figure 3).

Figure 3 Histopathological confirmation of thymolipoma (hematoxylin-eosin staining). (A) Low-power field (40×) showing a mixed distribution of mature adipose tissue (right) and benign thymic tissue islands (left). (B) High-power field (200×) of the thymic component revealing lymphocytes and characteristic Hassall’s corpuscles.

The patient recovered well postoperatively with immediate resolution of respiratory symptoms. The chest tube was removed on postoperative day 3, and the patient was discharged on postoperative day 7. Follow-up at 1 and 3 months revealed no symptoms, with chest radiography demonstrating complete lung re-expansion and no signs of recurrence (Figure 4).

Figure 4 Diagnosis and treatment timeline for the patient in this case.

Ethical consideration

All procedures performed in this study were in accordance with the ethical standards of the institutional and/or national research committee(s) and with the Helsinki Declaration 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.

Discussion

This case demonstrates the removal of a 19-cm thymolipoma via dual-port thoracoscopic surgery, vividly illustrating three core principles of contemporary thoracic surgery: precise diagnosis, refinement of minimally invasive techniques, and meticulous perioperative decision-making.

The cornerstone of preoperative diagnosis lies in the characteristic CT features of thymolipoma: predominantly fatty density, thin internal septa, flexible morphology, and conformity to mediastinal structures (1,4,9). Such classic presentations exhibit extremely high imaging specificity. The literature consistently emphasizes the limitations of percutaneous core needle biopsy for predominantly fatty mediastinal masses: it often yields non-diagnostic samples composed mainly of fat and cannot reliably exclude well-differentiated liposarcoma—a diagnosis dependent on identifying tissue structural heterogeneity, which limited biopsies frequently fail to capture (5,10). Furthermore, the procedure carries inherent risks. Therefore, for symptomatic lesions with typical benign imaging features, direct complete surgical resection—which simultaneously achieves definitive pathological diagnosis and curative treatment in a single procedure—is a well-supported and efficient strategy (10,11). When CT imaging raises uncertainty regarding the relationship with critical structures such as the pericardium or great vessels, cardiac-gated magnetic resonance imaging (MRI) is recommended as a follow-up modality due to its superior soft tissue contrast (9,12).

The conventional standard approach for large mediastinal mass resection is open thoracotomy, which provides optimal exposure but is associated with significant postoperative pain and prolonged recovery (5). Nevertheless, successful minimally invasive surgical resection of giant thymolipoma has been documented, demonstrating the feasibility of this approach for such large benign tumors (7). Although literature reports of multi-port (3–4 port) thoracoscopic resection of large thymolipoma exist (7,8), the application of dual-port technology represents a strategic breakthrough in further reducing trauma without compromising surgical principles. This case demonstrates that even a 19-cm tumor can be safely dissected through strategic incision planning and advanced thoracoscopic instrumentation. Key technical points include: (I) Incision planning strategy: a posterior viewing port provides a semi-thoracic panoramic view, while an anterior working port enables direct ergonomic manipulation of the anterior mediastinum. (II) Systematic hemostasis and dissection: Ultrasonic scalpels effectively establish clear anatomical planes around thymolipoma, combining precise cutting with simultaneous vascular sealing. Accurate identification and preservation of the phrenic nerves is non-negotiable. (III) Reliable vascular control: The ability to safely isolate, ligate, and transect large vascular pedicles near the aorta under thoracoscopic visualization demonstrates the advanced safety and efficacy of this technique when performed by experienced surgeons.

Removing large benign specimens poses the final technical challenge. Primary approaches include: extending the single-port incision for complete extraction (used in this case) or employing closed-bag intraoperative fragmentation techniques (13,14). Selection depends on tumor consistency, capsule integrity, and pathological specimen preservation principles. In this case, the tumor exhibited firm consistency and a robust capsule. Complete extraction via moderate incision extension proved both safe and straightforward, while ensuring optimal pathological assessment of the entire lesion. It must be emphasized that any fragmentation procedure should be performed only with high preoperative certainty of benignity and within a sealed, leak-proof retrieval system to completely eliminate the risk of intraoperative tissue dissemination, thereby directly addressing key safety concerns (13,14).

While the absence of MG symptoms in our patient is consistent with the typical presentation of thymolipoma, it is crucial to contextualize this finding. The association between thymolipoma and MG is notably low, occurring in only 2–9% of cases based on the largest published case series (1,3). These seminal reports from the 1990s remain the most comprehensive epidemiological data for this rare tumor, as subsequent literature has primarily consisted of isolated case reports without larger population studies. This low incidence stands in stark contrast to thymoma where MG is present in approximately 50% of patients (2). Although the lack of MG symptoms supports a benign diagnosis, it does not definitively exclude thymoma, as 30–50% of thymoma patients are MG-negative (11). Therefore, imaging characteristics remain the primary differentiator, with predominant fat attenuation being the key feature that makes thymoma unlikely in this case.

Thymolipoma are curable with complete resection alone, requiring no adjuvant therapy or long-term oncological follow-up (3,11). Thorough understanding of differential diagnoses is crucial for preoperative planning: (I) Mediastinal lipoma: purely fatty tumor lacking thymic parenchymal components. (II) Lipomatous degenerative hyperplasia of thymus: may show histological continuity with thymolipoma, but differs in being dominated by fatty stroma containing organized thymic tissue and Hassall’s corpuscles (15). (III) Mature teratoma: characterized by cystic areas, calcifications, and multiple embryonic layers. (IV) Thymoma: tumors originating from thymic epithelial cells; some cases contain fatty components but show no significant reduction in fat density on CT scans. (V) Differentiated liposarcoma: the most critical solid lesion to consider.

Conclusions

This case report demonstrates that giant thymolipoma—lesions once considered treatable only by open surgery—can now be successfully and completely resected using advanced dual-port thoracoscopic techniques. Key factors for success include: (I) definitive preoperative imaging diagnosis providing the basis for direct surgical intervention; (II) mastery of dual-port thoracoscopic surgical techniques, including the ability to perform reliable vascular control under endoscopic visualization; (III) Development of a personalized, safe specimen retrieval strategy. This approach maximizes the established advantages of minimally invasive surgery—including reduced postoperative pain, shorter hospital stays, accelerated recovery, and improved cosmetic outcomes—while adhering to the fundamental oncological principle of “complete resection”. For selected patients with large benign mediastinal tumors, this technique represents a significant advancement in surgical treatment.

Acknowledgments

None.

Footnote

Reporting Checklist: The authors have completed the CARE reporting checklist. Available at https://acr.amegroups.com/article/view/10.21037/acr-2025-299/rc

Peer Review File: Available at https://acr.amegroups.com/article/view/10.21037/acr-2025-299/prf

Funding: None.

Conflicts of Interest: All authors have completed the ICMJE uniform disclosure form (available at https://acr.amegroups.com/article/view/10.21037/acr-2025-299/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 performed in this study were in accordance with the ethical standards of the institutional and/or national research committee(s) and with the Helsinki Declaration 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/.

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