Accuracy of MRI-based delineation of mandibular bone invasion in oral squamous cell carcinoma using histopathological validation.

In oral squamous cell carcinoma (OSCC) with mandibular invasion, precise preoperative delineation of the tumour within bone is crucial for three-dimensional (3D) virtual surgical planning and postoperative outcomes. Magnetic resonance imaging (MRI) and computed tomography (CT) enable 3D delineation, but MRI often overestimates tumour size due to inflammation and peri-tumoral oedema, potentially leading to excessive resections and increased morbidity. A quantitative 3D analysis of overestimation by MRI is lacking. A postoperative pathological assessment workflow to determine delineation accuracy was developed in this study. Eight patients with OSCC who underwent mandibular resection were included. A guide enabled precise gross sectioning of resected mandibles, and the sections were analysed histopathologically for bone invasion and erosion. Delineation error was measured and expressed as the length of over-resected bone. MRI-based delineation overestimated tumour size in all patients, with a mean length of over-resected mandibular bone, omitting the 10-mm safety margin, of 32 ± 16 mm. Bone invasion and erosion were observed in six cases. This study highlights the need for improved imaging feedback. Overestimation from MRI may lead to excessive resection of healthy tissue. Enhanced imaging feedback is essential to support radiologists and surgeons in achieving more precise delineations and preserving healthy tissue.