50 patients with histologically proven squamous cell carcinoma of the oral cavity with doubtful invasion of the skin as assessed clinically by the principal investigator will be enrolled in the study.

The CT scan would be performed on 16 row MDCT (Multi Detector Computed Tomography) scanner with patient in supine position and after administration on intravenous iodine containing (300mg of iodine per ml) contrast. The scans would be performed from the root of the neck to the skull base with slice thickness of 2.5 mm, from the volume so acquired 0.625 thick slices would be generated for viewing in soft issue and bone algorithm and for multiplanar reformatting in coronal and sagittal planes.

From the images so generated, tumor dimensions including depth would be ascertained. Distance from the outermost edge of the tumor to the skin will be calculated by a senior radiologist. We also make a note of presence or absence and extent of fat stranding in the subcutaneous tissue, whether it (fat stranding) is reaching up to the skin and if there is skin thickening or infiltration by the lesion.

All these patients will be subjected to surgery and intraoperative decision to excise the skin will be taken by operating surgeon irrespective of the calculated distance between the tumor and the skin on CT scan. All resected specimens will be evaluated in accordance with a standardized protocol. This will entail recording the greatest antero-posterior (longitudinal) and medio-lateral (transverse) dimensions of the tumor in millimeters. The tumor will be sliced at 4-5 mm thickness, perpendicular to the tumor longitudinal axis. Maximum tumor thickness and the closest distance of the tumor from the skin (or the lateral soft tissue in cases where skin has not been removed) will be recorded. The tumor thickness, depth of invasion and distance from the overlying skin will be confirmed on microscopy. Presence of subdermal lymphatics and microscopic skin thickness will also be recorded.

Comparison between CT & Histopathological Report (HPR) findings

 The  CT scan  findings  will  be  compared  with

histopathological findings using SPSS version 18, Chicago IL USA. Correlation method will be used to compare different variables. The depth of invasion or the maximum tumor thickness on CT scan will be compared with the depth of invasion / tumor thickness reported by the pathologist. Similarly comparison would be made of tumor dimensions in antero–posterior and transverse plane between CT scan and HPR findings. The comparison of values obtained by calculating the distance between the tumor and the skin on CT scan and that of those reported by pathologist would be made using correlation method. For each patient absence or presence of fat stranding would be compared with absence or presence of subdermal lymphatic invasion by the tumor cells reported on histopathology.