Imiquimod and lymphatic field clearance: a new hypothesis based on a remote immune action on skin cancer

Basal cell carcinoma and actinic keratosis are frequent neoplasms. Topical treatments include the recently approved imiquimod cream. We describe here the case of a 68-year-old man with multiple actinic keratosis on the forehead, upper trunk and on the left cheek. In addition, an exulcerated basal cell carcinoma was observed. The patient was advised only to treat lesions on the forehead with imiquimod cream. This resulted in complete clearance of actinic keratosis within 6 weeks. At follow-up, a planned surgical excision of the basal cell carcinoma and actinic keratosis on the cheek was carried out. Histopathologically, both excision specimens no longer showed features of basal cell carcinoma or actinic keratosis, despite the fact that the imiquimod treatment was not applied to the cheek. Imiquimod cream is a topical immune response modifier, which has shown antiviral and anti-tumorous properties by inducing the production of cytokines as well as by stimulating dendritic cells and lymphocytes. Our observation supports the concept of lymphatic transport of immune cells and factors with subsequent immunological curing of tumours, not only in the treated area, but also those in the area between the imiquimod application site and the regional lymph nodes (the "lymphatic field clearance").