Early invasive squamous cell carcinoma recurrence rates: A study examining surgical margins, tumor surface diameter, invasion depth, and grade of differentiation in 1296 cases over 9 years

Background Invasive squamous cell carcinoma (SCC) is typically treated by surgical excision. Methods Consecutive SCC excisions were reviewed prospectively in a single Australian center from 2009 to 2017. Cases were examined for recurrence by histopathologic margins, microscopic tumor surface diameter, invasion depth, grade of differentiation, and anatomic site. Results Over 9 years, 1296 cases were collected. By grade of differentiation maximum average microscopic surface diameters ranged from 8.0 to 9.6 mm and maximum average depths from 1.3 to 2.5 mm. Minimum average histopathologic margins for well, moderate, and poorly differentiated SCC, respectively, were 1.4, 1.1, and 1.3 mm. Recurrence occurred in 1.7% of well (n = 18/1084), 1.8% moderate (n = 3/165) and 6.4% in poorly differentiated (n = 3/47) SCC. No recurrence occurred beyond a histopathologic margin of 3.5 mm for well and 2.5 mm for moderately differentiated SCC. Highest recurrence for well‐differentiated SCC by anatomic site was the lip (7.0%) then ear (4.6%). Conclusion We found a recurrence rate of 1.0% for histopathologic margins of 1.5 mm with early well‐differentiated SCC. The grade of differentiation and anatomic site had a larger influence on recurrence rates compared to the histopathologic margins. Poorly differentiated SCC and ear or lip sites require wider surgical margins.