Diffuse-type giant cell tumor of the tendon sheath in the temporal region incidentally diagnosed due to a temporal tumor: A report of two cases and review of the literature.

Diffuse-type tenosynovial giant cell tumor (D-GCTS) is a rare benign lesion that not only frequently occurs in the fingers, but also along the tendon sheaths of the foot and ankle. The present study reports the cases of two middle-aged patients that were diagnosed with D-GCTS. The presentation of the D-GCTS lesions was extremely rare, as the tumors were located in the temporal fossa and threatened the skull base and external auditory canal. There were similarities and differences between the two patients in their clinical symptoms, disease progressions and invading sites. The patients' disease course occurred unnoticed with the absence of pain, was protracted and became infiltrative. However, the female patient was admitted to the hospital due to the occurrence of pain in the left temporal region, and the male patient presented at the doctor due to a painless left temporal mass and external auditory canal bleeding. Therefore, the operation area of the two patients was not the same. This type of illness should be considered in the differential diagnosis for masses occurring in the temporal region. Total tumor removal is the best treatment for D-GCTS, and the careful monitoring of recurrence can achieve a good clinical outcome subsequent to the surgical resection.