https://orcid.org/0000-0003-4015-9385
Abstract
The metaplastic thymoma with giant multilocular-cyst formation had not been documented. The metaplastic thymoma is an extremely rare primary thymic epithelial tumor with an indolent clinical course. It is characterized by a histologic biphasic appearance, which is consisted of solid epithelial areas and spindle cells as the background. This specific pattern can be easily mistaken as the type A thymoma or the type A components of type AB thymoma. When cystic change occurs in metaplastic thymoma, it will bring more challenges for both imaging and pathological diagnosis. Herein, we reported an extremely rare case of a 14.9-cm giant tumor located in the anterior mediastinum of an elderly female. The tumor is consisted of both multilocular cysts and solid components, with the largest cyst measuring 6 cm in diameter. The multilocular cyst contained hemorrhage, calcification, and cholesterol crystal cracks without cell lining. In the solid area, the epithelial cell nests were surrounded by spindle cells with scattered lymphocytes. With immunostains, neither type of cells was CD20 positive. The epithelial cells were positive for CK and P63, while the spindle cells expressed vimentin and EMA. Fluorescence in situ hybridization analysis revealed that the tumor harbored YAP1-MAML2 gene fusions. Accordingly, although the multilocular cystic pattern set a diagnostic challenge, the diagnosis of metaplastic thymoma was rendered due to the immunohistochemistry staining and YAP1-MAML2 gene rearrangement detection.
Data Sharing Statement
The datasets supporting the conclusions of this article are included within the article.
Ethical Approval and Consent to Participate
Ethical approval for this study was obtained from the institutional ethic review boards of the First Affiliated Hospital of China Medical University.
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Informed consents were obtained from the patients for publication.
Author Contributions
All authors made a significant contribution to the work reported, whether that is in the conception, study design, execution, acquisition of data, analysis, and interpretation, or all these areas; took part in drafting, revising, or critically reviewing the article; gave final approval of the version to be published; have agreed on the journal to which the article has been submitted; and agree to be accountable for all aspects of the work.
Disclosure
The authors declare that there is no conflict of interest regarding the publication of this article.