Confirmation of histological clearance of superficial basal cell carcinoma with multiple serial sectioning and Mohs' micrographic surgery following treatment with imiquimod 5% cream

Background: Although the effectiveness of daily dosing regimens of 5% imiquimod cream for the treatment of superficial basal cell carcinomas (sBCC) has been documented by recent studies, concerns about long-term outcome remain. The majority of efficacy data is based on clinical clearance and limited histological examination which may not identify tumour presence at the periphery. Objective: To assess the efficacy of 5% imiquimod cream for sBCC using detailed histological assessment 1 year after completion of treatment. Methods: Nine individuals with biopsy-proven sBCC treated with 5% imiquimod cream 1 year previously and who remained clinically clear were recruited. Paraffin-embedded excision specimens from the original tumour site were extensively examined by a dermatopathologist. Examination and analysis of frozen sections of the original tumour perimeter using Mohs' micrographic surgery (MMS) were then performed. Results: Eight of nine individuals, 89% (95% CI 56% to 97%) were histologically clear of sBCC at 52 weeks. One individual had a single focus of sBCC at one lateral margin. Conclusion: The results show agreement between the clinical and histological assessment of tumour clearance. However, the persistence of disease in one patient, although limited, indicates the need for cautious long-term follow-up studies on the use of 5% imiquimod cream for sBCC.