BACKGROUNDIncomplete excision of squamous cell carcinoma (cSCC) is associated with an increased risk of recurrence, metastasis, and mortality.OBJECTIVETo determine the rate and characteristics of incompletely excised cSCC in a dermatological daily practice setting.METHODSProspective study of all patients who gave informed consent, with a cSCC treated with standard excision (SE) at 1 of 6 Departments of Dermatology in the Netherlands between 2015 and 2017. Pathological reports were screened to detect all incompletely excised cSCCs.RESULTSA total of 592 patients with 679 cSCCs were included, whereby most cases were low risk cSCC (89%). The rate of incompletely excised cSCC was 4% (n = 26), and the majority were high-risk cSCCs of which 24 invaded the deep excision margin.CONCLUSIONThis prospective study showed that in a dermatological setting, the risk of an incompletely excised cSCC is low (4%) for a cohort that was dominated by low-risk cSCCs. Most incompletely excised cSCCs were of high risk, and incompleteness was almost always at the deep margins. These results suggest that for high-risk cSCC, one should pay attention especially to the deep margin when performing SE, and/or microscopic surgery should be considered.