Adnexal cancerization in actinic keratosis and cutaneous Bowen's disease: Incidence, degree and clinical implications

Since actinic keratosis as well as Bowen's disease show high recurrence rates when superficially removed, the involvement of the adnexae as a potential source of local recurrence has been discussed. This study was designed to characterize the incidence, degree, features and clinical significance of adnexal cancerization in both neoplasms. Therefore, 252 actinic keratosis and 112 Bowen's disease specimens were histologically reviewed. In addition, 75 patients treated by curettage were followed up to assess the therapeutic results. Involvement of the appendages was demonstrable in each of the cases reviewed including folliculo-sebaceous as well as eccrine structures deep in the cerium. However, a distinct pattern of cancerization (basal versus complete cancerization) was evident which depended on both the kind of tumor as well as the kind of adnexal structure. In both tumor groups, proliferation involving the appendages extended significantly deeper into the cerium (e.g. hair follicles p < 0.005) than free, downward-proliferations : 11/65 actinic keratosis-patients (16.9%) and 1/10 Bowen's disease-patients revealed local tumor recurrence, if the mean depth of curettage was 0.42 mm and 0.75 mm, respectively. In a high number of actinic keratosis and Bowen's disease lesions, the involvement of the adnexae proved to be deeper than the average curettage (up to 43.2% and 23.4%, respectively). These results provide evidence that posttherapeutic tumor residues from cancerous adnexal structures may represent a major cause of local recurrences in superficially-treated actinic keratosis and Bowen's disease-patients.