Purpose <p>Recurrent diffuse-type tenosynovial giant cell tumor: Clinical presentation, Diagnosis, and Management.</p> Background <p>Tenosynovial giant cell tumor (TGCT), is a neoplasm arising from synovial joints, bursae, or tendon sheaths. The initial clinical symptoms are vague and non-diagnostic. Patients may present with non-specific complaints such as subtle joint discomfort or pain. As the lesion progresses, the joint range of motion will become limited resulting in swelling, effusion, stiffness, and hemarthrosis. According to the World Health Organization (WHO) classification, TGCTs are divided into two main subtypes based on their growth pattern: localized or diffuse. Diffuse-type TGCTs tend to be more aggressive.</p> Case presentation <p>An 82-year-old female presented with right facial swelling and discomfort. MRI showed a large mass centered in the right temporomandibular joint (TMJ) with erosive osseous changes at the skull base. Past medical history was significant for surgical resection of TGCT of the TMJ, 5 years earlier. The patient was subsequently seen by oral and maxillofacial surgery and neurosurgery and underwent a surgical resection. Histologic examination was consistent with a recurrent diffuse-type TGCT with chondroid metaplasia.</p> Discussion <p>The role of CSF1 protein over-expression in various synovial pathologies.</p>