Pigmented Villonodular Synovitis of the Infratemporal Fossa

A 35-year-old woman is referred to the otolaryngology clinic for evaluation of a palpable mass in the left preauricular region present for approximately 1 year prior to presentation. The mass is associated with intermittent swelling and tenderness, as well as headaches radiating along the left temporal region. Physical examination revealed a 1-cm, palpable, subcutaneous mass in the left preauricular region. MRI revealed a well-defined, enhancing mass measuring 19 mm in diameter. The mass is located anterosuperior to the left external auditory canal with evidence of erosion of the outer cortex of the petrous temporal bone.

Excision was performed under general anesthesia with facial nerve (cranial nerve VII) monitoring. Intraoperatively, a firm, soft tissue mass adherent to the temporomandibular joint (TMJ) capsule was identified. Erosion of the outer cortex of the temporal bone immediately superior to the infratemporal fossa was noted; therefore, this region was drilled down to the dura to ensure complete removal of the mass. Pathologic evaluation confirmed pigmented villonodular synovitis (PVS). The patient's case was reviewed at the multidisciplinary head and neck tumor board, where recommendations were for postoperative proton therapy due to close margins of excision and adjacent soft tissue invasion.

PVS is a benign, yet locally destructive lesion arising from the synovial tissue of joints, tendon sheaths, and bursae. More than 80% of the lesions arise from the knee joint. Disease progression can range from slow growth with compression of adjacent structures to rapidly expansile lesions with destruction of adjacent bone including the skull base. PVS of the TMJ is exceedingly rare, with less than 35 reported cases since the disease entity was initially described in 1941. Extra-articular lesions, as in this case, are less frequently reported as most lesions involving the TMJ have evidence of mandibular destruction. This case report will discuss the incidence of PVS, with review of the literature pertaining to radiologic characteristics, surgical management, and differential diagnosis of infratemporal masses. Further awareness of this disease entity among the head and neck surgery community is crucial because failure to accurately diagnose the condition leads to inappropriate treatments and progression of disease.