Resection of shrinking secondary thymic cyst during follow-up—a case report

Introduction

Thymic cysts can be classified as congenital or acquired. Congenital cysts are typically thin-walled unilocular lesions, whereas acquired thymic cysts are typically thick-walled multilocular lesions (1). Most thymic cysts do not change in size over a short period of time.

Thymic cyst rupture rarely occurs; however, when it does happen, it is associated with serious complications, such as mediastinal hemorrhage or hemothorax (2). We experienced a case of partially ruptured thymic cyst without symptoms or complications. We present this article in accordance with the CARE reporting checklist (available at https://med.amegroups.com/article/view/10.21037/med-24-13-rc).

Case presentation

A 60-year-old woman visited Inje University Sanggye Paik Hospital with an abnormality detected during routine chest radiography. Chest radiography revealed a bulging contour in the left hilar region (Figure 1). Chest computed tomography (CT) with contrast enhancement revealed a 6 cm well-defined cystic mass in the prevascular mediastinum (Figure 2A,2B). There were multiple septations in the inferior portion of the cyst, and both the wall of the cyst and septa were enhanced. As the patient was asymptomatic and laboratory findings were unremarkable, we suspected an acquired thymic cyst rather than an abscess. Incidentally, a mixed ground-glass nodule (GGN) was detected in the right middle lobe (RML). Three months later, the patient underwent a follow-up CT scan with contrast enhancement for the GGN. On the follow-up CT scan, the 2 cm mixed GGN in the RML was stable. However, the prevascular mediastinal mass had changed in size and shape (Figure 3A,3B). The size of the mass decreased from 6 to 5 cm, and the attenuation of the internal fluid content increased, suggesting a complication. Furthermore, the lower part of the mass transformed into to a solid component and exhibited enhancement. The possibility of a malignant tumor in the prevascular mediastinum could not be ruled out. Thus, video-assisted thoracoscopic surgery (VATS) was performed. After surgery, the patient was discharged and is currently doing well.

Figure 1 Chest radiograph shows bulging contour at the left hilar area (arrows) with hilar overlay sign.

Figure 2 CT scans reveal a well-defined cystic lesion (asterisk in A) with an enhanced wall (arrowheads in A) in the left prevascular mediastinum. A small septum is suspected at the inferior portion of the cystic mass (arrow in B). CT, computed tomography.

Figure 3 Follow-up CT scans reveal that the size of the cystic mass was decreased. The attenuation of the internal fluid is increased (asterisk in A), and the far inferior portion of the mass has changed to a solid component (arrow in B). CT, computed tomography.

A surgical examination revealed a large cystic mass in the left prevascular mediastinum. Adhesion to the lung and aorta was observed, but they were relatively well separated (Figure 4).

Figure 4 Thymectomy specimen image shows a 5 cm sized cyst (asterisk) in the upper portion of the left lobe of the thyroid gland. Grossly, no rupture was noted.

Upon gross macroscopic examination, the mass appeared as a 5 cm encapsulated cystic mass. The inner surface of the mass was relatively smooth, with yellowish plaques. The surrounding tissue exhibited creamy-yellowish necrotic changes. The pathological examination revealed a partially ruptured thymic cyst with fat necrosis and multifocal granulomas.

Ethical statement

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 (as revised in 2013). Publication of this case report and accompanying images was waived from patient consent according to the Sanggye Paik Hospital institutional review board.

Discussion

There are controversies in the treatment of thymic cysts (3,4). Some clinicians prefer strict medical supervision, while others advocate immediate excision to establish a diagnosis and prevent complications. However, if there is a change in the imaging findings during follow-up, it is possible that it has transformed into a malignant condition, necessitating surgery (5).

Thymic cyst rupture is reported very rarely; however, when it occurs, it is accompanied by a variety of complications. In Tsuda et al.’s report, the ruptured thymic cyst presented with mediastinal hemorrhage and hemothorax (6). Upon histopathological examination, a hematoma observed due to partial destruction of the epithelial lining. And in Lachanas et al.’s report, the thymic cyst ruptured into the pleural cavity (7). Our patient had neither symptoms nor complications. However, if the operation is delayed, complications, such as fluid leakage from the thymic cyst into the pleural cavity due to overt rupture, and formation of a hematoma and hemothorax, could occur.

Conclusions

In conclusion, this decrease in size may also lead to an increase in the solid portion of the thymic cyst, potentially signaling early rupture. However, additional investigations and analyses are necessary to confirm this hypothesis.

Acknowledgments

Funding: None.

Footnote

Reporting Checklist: The authors have completed the CARE reporting checklist. Available at https://med.amegroups.com/article/view/10.21037/med-24-13/rc

Peer Review File: Available at https://med.amegroups.com/article/view/10.21037/med-24-13/prf

Conflicts of Interest: Both authors have completed the ICMJE uniform disclosure form (available at https://med.amegroups.com/article/view/10.21037/med-24-13/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 (as revised in 2013). Publication of this case report and accompanying images was waived from patient consent according to the Sanggye Paik Hospital institutional review board.

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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