Cutaneous squamous cell carcinoma (cSCC) is a common malignancy, generally cured by surgical excision. A minority of such tumours recur, metastasize or even cause death. The 2021 British Association of Dermatologists (BAD) guidelines outline high-risk features that are used to guide the follow-up of patients after a primary cSCC. The aims of this study were to identify histological features of cSCC that are significantly associated with the development of complications, and to compare the sensitivity, specificity and number of appointments required to follow-up patients using different follow-up criteria. In total, 556 cases of primary invasive cSCCs excised between January 2014 and March 2018 were included and followed-up for a minimum of 4 years. Five per cent (n = 26) of tumours were associated with at least one cSCC-related complication, namely, local recurrence 3.8% (n = 21), nodal metastasis 1.6% (n = 9), distant metastasis 0.4% (n = 2) and disease-specific death 0.7% (n = 4). The initial diagnosed complication was local recurrence in 20 of 26 cases. Only two patients had the first complication beyond 2 years of the original cSCC. Factors that were statistically significantly associated with the development of a complication (P < 0.001) are larger diameter, larger depth of invasion, tumour invasion beyond the dermis, perineural invasion (irrespective of size), lymphovascular invasion, gross bone erosion and deep margin < 1 mm. Differentiation and peripheral margin were not significantly associated with complications. Therefore, it may be proposed that patients with tumours with at least one of the following risk factors be followed-up: diameter > 40 mm; depth of invasion > 6 mm; invasion beyond the dermis; presence of perineural or lymphovascular invasion or deep margin < 1 mm. In adopting these criteria, 739 appointments in 156 patients would be required over 2 years (4 monthly during the first year and 6 monthly during the second year). Twenty of the patients who developed a complication would be followed-up (sensitivity 76.9%, specificity 69.4%). Using the BAD guidelines, up to four more patients with complications would have been followed-up (sensitivity 92.3%, specificity 44.7%), but this would have required a total of 1556 follow-up visits in 242 patients. Given the limited resources, patient burden and the fact that local recurrence is most often the first complication, it may be reasonable to offer routine follow-up only to patients who have at least one of the proposed criteria. Coupled with patient education, this strategy could greatly reduce the number of follow-up visits required. Such a strategy may allow resources to be utilized to reduce waiting times, particularly for 2-week wait referrals, decreasing the delay in new skin cancer diagnoses.

Cutaneous squamous cell carcinoma (cSCC) is a common malignancy, generally cured by surgical excision. A minority of such tumours recur, metastasize or even cause death. The 2021 British Association of Dermatologists (BAD) guidelines outline high-risk features that are used to guide the follow-up of patients after a primary cSCC. The aims of this study were to identify histological features of cSCC that are significantly associated with the development of complications and to compare the sensitivity, specificity and number of appointments required to follow-up patients using different follow-up criteria. In total, 556 cases of primary invasive cSCCs excised between January 2014 and March 2018 were included and followed-up for a minimum of 4 years. Five per cent (n = 26) of tumours were associated with at least one cSCC-related complication, namely, local recurrence 3.8% (n = 21), nodal metastasis 1.6% (n = 9), distant metastasis 0.4% (n = 2) and disease-specific death 0.7% (n = 4). The initial diagnosed complication was local recurrence in 20 of 26 cases. Only two patients had the first complication beyond 2 years of the original cSCC. Factors that were statistically significantly associated with the development of a complication (P < 0.001) were larger diameter, larger depth of invasion, tumour invasion beyond the dermis, perineural invasion (irrespective of size), lymphovascular invasion, gross bone erosion and deep margin < 1 mm. Differentiation and peripheral margin were not significantly associated with complications. Therefore, it may be proposed that patients with tumours with at least one of the following risk factors be followed-up: diameter > 40 mm, depth of invasion > 6 mm, invasion beyond the dermis, presence of perineural or lymphovascular invasion or deep margin < 1 mm. In adopting these criteria, 739 appointments in 156 patients would be required over 2 years (4-monthly during the first year and 6-monthly during the second year). Twenty of the patients who developed a complication would be followed-up (sensitivity 76.9%, specificity 69.4%). Using the BAD guidelines, up to four more patients with complications would have been followed-up (sensitivity 92.3%, specificity 44.7%), but this would have required a total of 1556 follow-up visits in 242 patients. Given the limited resources, patient burden and the fact that local recurrence is most often the first complication, it may be reasonable to offer routine follow-up only to patients who have at least one of the proposed criteria. Coupled with patient education, this strategy could greatly reduce the number of follow-up visits required. Such a strategy may allow resources to be utilized to reduce waiting times, particularly for 2-week wait referrals, decreasing the delay in new skin cancer diagnoses.

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