Background: The new AJCC classification has highlighted some particular risk factors for squamous cell carcinoma (SCC) relevant for prognosis. Incomplete excision is not infrequent in SCC. The aim of this study is to examine features that can predict an incomplete excision on the basis of the new AJCC classification and to review the literature on this topic. Materials and Methods: 81 SCC patients were included. All patients were submitted to excisional biopsy with a margin of at least 4 mm from the clinical edges as recommended. Histological characteristics of the lesions analysed were maximum diameter, grading, site, Breslow thickness, Clark level, deep tissue invasion (neural, bone, muscle), presence of ulceration and positivity of the margins. Results: The average Breslow thickness was 3.93 mm. Out of the 81 patients included, 14 showed involved margins. The 2 parameters that were implicated in predicting involvement of the margins in the multivariable model were Breslow thickness and location of the lesion on the ear or lip. Grading was not associated with involvement of margins. Conclusion: According to the new AJCC classification, this study could be useful to plan the most suitable surgical technique in order to avoid the risk of incomplete surgery.