Diffuse giant cell tumors of the tendon sheath in temporomandibular joint: Two case reports and review of the literature.

Rationale: Diffuse giant cell tumors of the tendon sheath (GCT-TS) in the temporomandibular joint (TMJ) are extremely rare. Patient concerns: We reported the imaging appearance and the pathological findings of 2 male cases with diffuse GCT-TS in the TMJ (52 years for the case 1 and 50 years for the case 2) who complain of the hearing disorders of left ear when presenting to our hospital. Diagnosis: Preoperative computerized tomography (CT) scan revealed an irregular mass in the left temporal fossa with the sizes of approximately 5.8 x 3.8 x 4.6 cm for case 1 and 4.2 x 3.2 x 4.3 cm for case 2, respectively. Magnetic resonance imaging (MRI) findings showed a mass of 6.1 x 4.0 x 5.1 cm and 5.3 x 3.6 x 3.3 cm, respectively. Postoperative pathological examination revealed the diffuse multinucleated giant cells accompanied with synovial cells in the diffuse arrangement. Immunohistochemical examination showed CD68 (+), Vim (+), S-100 (-) and 2% of Ki-67 proliferation index. These characteristics are in line with the diagnosis of the diffuse GCT-TS in the TMJ. Interventions: Both cases underwent the gross total resection followed by radiation therapy. Outcomes: Two patients experienced no recurrence after follow-up of 1 to 2 year(s). Lessons: Diffuse GCT-TS in the TMJ is very rare. Clinicians should keep in mind the possibility of the GCT-TS when aggressive lesions involve the TMJ and adjacent bone destruction was found. Careful pre-and postoperative examinations and complete resection are the factors that lead to its optimal treatment, significantly reducing its recurrence rate.