Background: Obtaining adequate surgical margins, free of tumor, is crucial for success in oncologic surgery. The head and neck surgeon often finds that the tumor-free margin reported from histopathologic measurement is significantly smaller than the margin measured in-situ. It was the purpose of this study to quantify the change in size of mucosal and muscle surgical margins following excision, formalin fixation, and slide preparation of tongue and labiobuccal tissue in a canine model.
Methods: Ten mongrel dogs under general anesthesia for a concurrent project were used in this study. Changes in mucosal and muscle dimensions around custom-made brass disks, one with a needle depth gauge, were measured immediately following excision after formalin fixation and after slide preparation.
Results: The mean shrinkage from initial resection to final microscopic assessment of the lingual surface mucosal margins was 30.7% (p < 0.0001). The deep tongue margin shrank 34.5% (p < 0.0001). The mean shrinkage of the labiobuccal mucosal margin was 47.3% (p < 0.0001). In all cases, the greatest proportion of shrinkage occurred immediately upon resection.
Conclusions: From the in-situ measurement by the surgeon to final pathologic evaluation on the microscope slide, the measured dimensions of oral cavity mucosal and tongue muscle margins shrink significantly. To obtain 5 mm of pathologically clear margin an in-situ margin of resection of at least 8 to 10 mm needs to be taken. Studies reporting clinical correlation of recurrence and survival information with surgical margin status should include a detailed description of the technique used to determine the reported surgical margin status.