[Evaluation of shrinkage of surgical margins on tongue specimens following formalin fixation]

This study aims to evaluate the alterations in distances to the surgical margins on sheep tongue specimens, through resection, formalin fixation, frozen section, and microscopic examination.

Fifty fresh sheep tongues were used in the study. A metal plate was fixed on the lateral aspect of each tongue to represent tumor tissues. A total of 40 specimens with either 1 cm or 2 cm distances as surgical safety margins of the surrounding plate were prepared using either scalpel or monopolar cautery (10 specimens were prepared for each group). Additional 10 specimens with 1 cm safety margins were prepared using either scalpel or monopolar cautery (5 specimens per group) for frozen section examination. Distances to the metal plates before resection were compared with the ones which were determined after resection, frozen section examination, 24-hour formalin fixation and microscopic examination.

Distances to the surgical margins were found to be decreased in all specimens after resection, 10% formalin fixation and microscopic examination. The distances to the surgical margins were observed to be reduced by 6.5-7.5% on average after resection, 10-12% on average after formalin fixation and 30% on average after microscopic examination, compared to the baseline values. The level of shrinkage was reduced by 6.3-10% following microscopic section preparation during frozen section examination.

Seven to eight-millimeter distance to the surgical margin at minimum should be maintained to achieve a 5 mm in height surgical safety margin during sheep tongue resection. The distance defined by the pathologist may be multiplied with 1.42 to estimate around in-situ distance to the surgical margins. Therefore, 1.42 may be used as a corrective factor for sheep tongue tissues.