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Giant Multilocular-Cystic Metaplastic Thymoma: A Case Report
Lihua Han1, Bo Gao2, En-Hua Wang3
1The Central Laboratory of Morphology, Shenyang Medical College, Shenyang, People's Republic of China.
Pharmacogenomics and Personalized Medicine
|May 25, 2023
Summary
This study documents a rare giant metaplastic thymoma with multilocular cysts. YAP1-MAML2 gene fusions were identified, aiding diagnosis in this challenging case.
Area of Science:
- Pathology
- Oncology
- Genetics
Background:
- Metaplastic thymoma is an extremely rare primary thymic epithelial tumor.
- It presents with a biphasic histology of epithelial and spindle cells, often mistaken for Type A thymoma.
- Cystic changes in metaplastic thymoma pose diagnostic challenges.
Observation:
- A 14.9-cm giant metaplastic thymoma with multilocular cysts was observed in an elderly female.
- The tumor exhibited solid components and large cysts containing hemorrhage, calcification, and cholesterol crystals.
- Histopathology revealed epithelial nests surrounded by spindle cells and scattered lymphocytes.
Findings:
- Immunohistochemistry showed epithelial cells positive for CK and P63, and spindle cells positive for vimentin and EMA.
- Neither cell type was CD20 positive.
- Fluorescence in situ hybridization detected YAP1-MAML2 gene fusions, confirming the diagnosis.
Implications:
- This case highlights the diagnostic challenges of giant metaplastic thymoma with cystic formation.
- Immunohistochemistry and genetic analysis (YAP1-MAML2 gene fusion) are crucial for accurate diagnosis.
- Understanding these rare thymic tumors improves diagnostic accuracy and patient management.
