An unusual case of giant cell tumour involving the middle cranial fossa, originating from soft tissues of the temporomandibular joint.

A rapid onset swelling in the left temporomandibular joint(TMJ) region occurred in a 70-year-old man. The remoteclinical history was unremarkable; crepitus at the involvedTMJ, omolateral tinnitus, hearing decrease and persistentheadache in the sovraorbital area was reported. A firm masswas palpable intra- and extra-orally. Laboratory investigationswere within normal limits.Computed tomography (CT) and magnetic resonanceimaging (MRI) demonstrated a 2.5-cm ovoidal mass in theinfratemporal fossa (IF), which eroded the middle cranialfossa and emerged in an extradural location (Fig. 1a-c).A craniotomy was performed; the cut off of the zygomaticbone and the removal of the upper arm of the jaw allowed theexposure of the IF fully occupied by the neoplasm, whicheroded the floor of the middle cranial fossa; the intactoverlying dura was preserved. Tumour dissection was extendedto the anterior cranial fossa and the ovale foramen, invadedby the tumour; the rotundum foramen was uninvolved.Histological examination showed (Fig. 1d-e) abundantgiant cells with an osteoclast-like appearance, strong CD68positivity, a large number of centrally located nuclei andabundant eosinophilic cytoplasm. Numerous ovoid tospindle-shaped stromal cells with a thin rime of eosinophiliccytoplasm were also present, as well as several foci ofhaemosiderin pigment deposition and no areas of necrosis.Mitotic figures were scarce and without atypia. Thelabelling index (Ki67) was <30% and predominant in theosteoclast-like cells. The diagnosis was: giant cell tumour(GCT). Chest radiograph excluded pulmonary metastases.At 3-years follow-up there was no evidence of recurrence.