Clinical triage of cutaneous squamous cell carcinoma and basal cell carcinoma to avoid treatment delay: value of an electronic booking system.

BACKGROUND: Provisional clinical diagnosis is the first step in planning skin surgery. Different clinical priorities are given to basal cell carcinoma (BCC), squamous cell carcinoma (SCC) and malignant melanoma (MM). Discriminating between SCC and BCC can be difficult. The rate of misdiagnosis of SCC as BCC is reported as 5.7-87.6%, and can cause treatment delay. We have developed a web-based surgery booking system that requires clinical commitment to a putative differential diagnosis category, rather than a single diagnosis, at the time of consultation. This includes a crucial overlap category of 'SCC or SCC/BCC'.

AIM: To assess whether our system helped avoid treatment delay to patients with SCC, and to measure the number needed to treat (NNT).

METHODS: This was a retrospective analysis from April 2012 to August 2013, comprising all patients undergoing booked excisional surgery in our unit. The clinical triaging category was compared with the histological diagnosis. Sensitivity, specificity, positive predictive value, negative predictive value (NPV), NNT and mean Breslow thickness were calculated.

RESULTS: In total, 1455 lesions were excised, identifying 789 (54.2%) invasive malignancies (86 MM, 115 SCC, 583 BCC, 5 other), 100 in situ lesions and 150 dysplastic lesions. The majority (83.2%) of malignancies were designated into the correct malignant category. Misdiagnosis of SCC as BCC was 5.2%. Sensitivity and NPV for SCC were 94.8% and 99.4%, respectively. NNT was 1.26, 4.12 and 3.19 for BCC, SCC and MM respectively, and 1.73 for all malignancies. Mean invasive Breslow thickness was 1.29 mm [0.78 mm including melanoma in situ (MMIS)], and the MM to MMIS was 1.6.

CONCLUSION: An overlap triage category of 'SCC or SCC/BCC' helps to prevent delay in the treatment for patients with SCC.