Endobronchial pulmonary metastasis in malignant tenosynovial giant cell tumor: A rare cause of central airway obstruction.

Tenosynovial giant cell tumor (TGCT) is a rare mesenchymal neoplasm arising from the synovium, tendon sheath, or bursa. Although the localized and diffuse forms of TGCT are typically considered benign, malignant TGCT characterized by marked histologic atypia and increased mitotic activity may exhibit aggressive clinical behavior. Pulmonary metastasis from malignant TGCT is rare and, in previously reported cases, pulmonary involvement has predominantly been described as parenchymal nodules or pleural lesions. In this article, we describe a rare case of endobronchial pulmonary metastasis occurring approximately 72 months after the initial diagnosis of malignant TGCT originating from the tendon sheath of the knee.