Effect of Formalin Fixation on Surgical Margins in Patients With Oral Squamous Cell Carcinoma.

PURPOSE: Formalin fixation causes shrinkage of surgical margins, which can result in the underestimation of tumor-free margins. The purpose of this study was to show the effect of formalin fixation on surgical margins. Another aim of this study was to evaluate surgical margin shrinkage after fixation of oral squamous cell carcinoma (OSCC) specimens of the gingivobuccal sulcus (GBS).

MATERIALS AND METHODS: This was a cross-sectional study. The study sample consisted of OSCC specimens of the GBS after composite resection. The primary predictor variable was the length of the linear margin at various locations (anterior, posterior, medial, and lateral). The primary outcome variable was the percentage of change in each respective margin (anterior, posterior, medial, and lateral) after fixation in 10% formalin for 24 hours. Other variables were age, gender, use of smokeless tobacco, smoking status, and tumor staging. The difference between pre-fixation and post-fixation data was calculated using paired t test.

RESULTS: The sample consisted of 15 patients (7 men and 8 women; age range, 55 to 65 yr) diagnosed with OSCC of the GBS. Shrinkage of surgical margins (decrease) occurred after fixation compared with margins before fixation. The average surgical margin shrinkages were 18.7% anteriorly, 14.9% posteriorly, 23.6% medially, and 23.9% laterally. This shrinkage was statistically significant (P < .001).

CONCLUSION: Formalin fixation causes considerable shrinkage of surgical margins. This phenomenon should be considered by the pathologist before providing the final histopathology report.