Presentation
Pain in the left temporal bone region, left sided TMJ stiffness and facial nerve palsy.
Patient Data
Craniofacial CT scan revealed a radiolucent/osteolytic lobulated mass in the left temporal bone involving the TMJ surface and the sphenoid bone (ala major) with expansive growth and sharp margins. The cortex is expanded, severely thinned and partially destroyed, with irregular rim calcifications and "soap bubbles" structures, but without periosteal reaction.
Axial scan acquired during biopsy with the needle in situ.
MR imaging demonstrates a solid inhomogeneous component with predominantly low T1-weighted signal and low to intermediate T2-weighted signal. Within this solid tumor mass small multilocular cystic components with high T2-weighted signal and SWI signal loss due to calcifications can be observed. MR C+ imaging revealed inhomogeneous and septal enhancement in the solid component.
The tumor consists of polygonal chondroblasts with oval or grooved nuclei with well-defined cell border. Some multinucleated clusters of round histiocytes, spindle-shaped fibroblasts, foam cell transformed macrophages/ siderophages and giant cells were also observed. The mononuclear elements are epitheloid and PAS positive. A cartilage matrix/chondroosteoid formation can be observed in some areas with iron pigment. Immunohistochemically, the tumor cells are positive for S-100 protein.
Case Discussion
This case demonstrates a chondroblastoma ("Codman tumor") in a very unusual localization.
Temporal bone chondroblastomas are rare benign osseous tumors with very low prevalence (1-2%). They can be commonly found in all bones with endochondral ossification, but mostly in the epiphysis and/or metaphysis of long bones in young patients (2nd decade). The growth pattern of chondroblastoma differs from other entities affecting the temporal bone and should be differentiated from other temporal bone lesions. The patients usually complain of pain in the area, swelling and neurological symptoms such as facial nerve palsy. Common imaging modalities are CT and MRI. Microscopic and immunohistochemical analysis complete the diagnosis.
Differential diagnoses are clear cell chondrosarcoma, chondromyxoid fibroma and giant cell tumor. Furthermore eosinophilic granuloma (Langerhans cell histiocytosis) and enchondroma. Specific for the temporal bone lesions are: confluent apical petrositis, cholesterol granuloma, plasmocytoma and temporal bone rhabdomyosarcoma.
The treatment approach differs depending on the location of the tumor and on the grade of the expansive/destructive pattern.
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