Invasion of the mandible in gingivobuccal complex cancers: Histopathological analysis of routes of tumour entry and correlation with preoperative assessment.

OBJECTIVES: To determine the most accurate imaging modality predicting mandibular invasion in gingivobuccal (GB) complex cancers. To determine patterns of invasion and routes of tumour entry into the mandible by detailed histopathologic analysis. MATERIAL AND METHODS: Prospective observational study of GB Complex cancers juxtaposed with the mandible clinically necessitating some form of mandibular resection. Orthopantomogram (OPG), Multi Detector Computed Tomography (MDCT), DENTA scan and Single Photon Emission Computed Tomography scan (SPECT) were performed after which the patient was subjected to surgery. Histopathological assessment was systematically performed with serial cuts of the mandibular segment. RESULTS: Of 70 patients, MDCT was the most accurate with area under curve (AUC) of 0.833. OPG, DENTA and SPECT had AUC of 0.714, 0.786 and 0.738 respectively. Mean calculated difference of involved height was -0.025 cm by MDCT (p value 0.87), -0.2 cm by OPG (p value 0.09) and 0.12 by DENTA scan (p value 0.41). Mean difference of involved length was -0.51 cm (p value 0.08) and -1.02 cm (p value 0.04) for MDCT and OPG respectively. 50% of tumour invasion was through the occlusal route while large tumours demonstrated multiple routes of entry. CONCLUSION: -Gingivobuccal complex cancers are homogenous with respect to mandibular invasion, preferred route of tumour entry being the occlusal surface. -Multidetector CT scan is fairly accurate in detecting mandibular involvement and predicting extent of involvement. -Oncological safety can be achieved by positioning the bone cuts corresponding to the adjacent soft tissue margins in segmental mandibulectomy.