Presentation
Progressive onset of left-sided jaw pain and swelling.
Patient Data
Large soft tissue mass involving the proximal aspect of the masseter muscle, medial aspect of the lateral pterygoid muscle, temporalis muscle as well as destruction of the left temporal bone. Soft tissue opacification in the mastoid air cells of the mandibular fossa. Associated intracranial mass with small cystic focus suggestive of necrosis.
Small reactive focal bone spur and degenerative change in the anterior aspect of the left mandibular condyle.
Internal auditory canals are both symmetrical. Right temporomandibular joint demonstrates normal alignment and joint space. No definite enlarged nodes in the proximal aspect of the neck.
Conclusion:
Destructive lesion of the left temporal bone and large soft tissue mass with involvement of the infratemporal fossa and middle cranial fossa. Mild reactive bony spur at the anterior aspect of the left mandibular condyle.
Soft tissue mass with heterogenous enhancement involving the left infratemporal fossa and adjacent anterior margin of the left temporomandibular joint. It is extending at the inferior aspect into the pre-auricular region deep to the parotid gland.
There is also extension into the left skull base at the left middle cranial fossa and there is associated dural thickening and enhancement overlying the left temporal lobe. No change in cortical or subcortical T2/FLAIR signal. Except for small locules of high signal along the intracranial component of the lesion there is predominantly low signal on T2-weighted sequence.
Conclusion:
Large soft tissue mass lesion of the left infratemporal fossa infiltrating at the superior aspect into the left middle cranial fossa and at the inferior aspect into the pre-auricular region.
Based on the imaging features differentials include a tumor with fibrous characteristics such as fibrosarcoma, a hemorrhagic lesion such as telangiectatic osteosarcoma or a lesion directly involving the left temporomandibular joint such as pigmented villonodulae synovitis.
Case Discussion
The patient underwent a craniofacial resection of the large infratemporal fossa lesion.
Histology
MICROSCOPIC DESCRIPTION: Fragments of bone, fibrous tissue and osteoid are surrounded by a cellular proliferation composed of two distinct components. Large numbers of multinucleate giant cells are scattered throughout the lesion in a background of closely packed polyhedral cells with oval nuclei, small nucleoli and moderate amounts of pale cytoplasm. Large amounts of hemosiderin pigment is present within cell cytoplasm and extracellularly. Up to 3 mitoses per 10 high power field are identified. There is no necrosis. Ki67 proliferation index is less than 5%.
- Positive
- CD68
- S100
FINAL DIAGNOSIS: Giant cell lesion
Pigmented villonodular synovitis (PVNS) is a benign proliferative disorder of the synovium. It predominantly presents with monoarticular involvement of large joints such as the knee and hip joints, however, in rare cases it may affect the temporomandibular joint with invasion of the middle cranial fossa 1-3.
The exact cause of PVNS remains unknown but it may be due to chronic inflammatory process or recurrent intra-articular hemorrhage following trauma 1,2.
PVNS with high iron content will demonstrate non-calcified soft tissue lesion with increased attenuation. Depending on the stage of progression there may be potentially significant invasion and destruction of the surrounding bony structure on CT imaging 1,4. On MRI there will typically be low to intermediate signal intensity on both T1-weighted and T2-weighted sequences (due to the deposition of hemosiderin) 1,2.
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