Tenosynovial Giant Cell Tumor in an Infant

In this report, the authors describe a child presenting at 6 months old with a rapidly expanding extracranial left temporal mass concerning for malignancy. The mass was successfully treated at 16 months with radical surgical excision. The patient was found to have a tenosynovial giant cell tumor, diffuse type, completely encased by the temporalis muscle. To our knowledge, this is the first report of a case of diffuse type tenosynovial giant cell tumor in the temporalis muscle, without articular involvement, presenting in an infant.