Sarcomatoid Thymic Carcinoma With YAP1::MAML2 Fusion Transformed From Metaplastic Thymoma

This is the authors' abstract. We don't add key points for this paper.

Metaplastic thymoma is a rare thymic epithelial tumor characterized by biphasic histology and the YAP1::MAML2 gene fusion. Although typically indolent, rare tumors with high-grade transformation have been reported. We present the fifth reported patient with metaplastic thymoma with high-grade transformation and the first patient with thymic sarcomatoid carcinoma with molecularly proven YAP1::MAML2 fusion. The aggressive clinical behavior and dismal prognosis underscore the need for molecular characterization of thymic sarcomatoid carcinomas, as this may have implications for future targeted therapies and potentially identifies underrecognized tumors with high-grade transformation from metaplastic thymoma.