An unusual presentation of intraosseous malignant peripheral nerve sheath tumour of mandible.

Malignant peripheral nerve sheath tumour (MPNST) is a rare mesenchymal tumour which usually presents high grade malignancy. We report an atypical case of intraosseous malignant peripheral nerve sheath tumour on mandible in a 36-year-old male. Patient presented with an incidentally discovered radiolucency on the left anterior mandible and did not complain of any symptoms. Panoramic radiograph and computed tomography showed enlargement of inferior alveolar nerve canal, thinning of the cortex and calcified foci within an expansile mass. Magnetic resonance images revealed heterogeneous hyperintense signal intensity with a well-defined margin on T2 weighted images, heterogeneous enhancement on contrast-enhanced T1 weighted images and intermediate signal intensity and inferior alveolar nerve canal enlargement on T1 weighted images. In spite of benign radiologic characteristics as mentioned above, histopathologic examination of biopsied specimen otherwise revealed a low-grade malignancy. Wide excision of mandible was performed and there has been no loco-regional recurrence or distant metastasis over 1 year following surgery. This case indicates that, even when imaging modalities clearly demonstrate benign nature of intraosseous neurogenic tumour, care must be taken to establish proper treatment plan for assumed malignancy with a definitive histopathological analysis.