Tenosynovial giant cell tumor around the rectus femoris tendon mimicking a malignant bone tumor: A case report

Tenosynovial giant cell tumor is a benign soft tissue tumor that most commonly occurs in the synovium of joints, bursae, and tendon sheaths. Imaging characteristics may lead to the misdiagnosis of tenosynovial giant cell tumor as cancer metastases. We describe a rare case of localized type tenosynovial giant cell tumor occurring around the attachment of the rectus femoris tendon with bone destruction at the anterior inferior iliac spine. This case report describes a man in his late 50s who underwent fluorodeoxyglucose positron emission tomography/computed tomography for follow-up of tongue cancer. Fluorodeoxyglucose uptake in the left anterior inferior iliac spine suggested a metastasis from tongue cancer. However, the pathological diagnosis of the tumor, which was obtained via core needle biopsy, was tenosynovial giant cell tumor. It is important to make an appropriate diagnosis of tenosynovial giant cell tumor using biopsy, if necessary. Careful preoperative examination is a key factor in the optimal treatment of this tumor.