Background: Diffuse epidermal and periadnexal squamous cell carcinoma in situ (DEPS) is a condition in which large areas of skin are affected by atypical keratinocytes that grow beneath the epidermis and encase adnexal epithelia. Normal differentiation of the overlying epidermis and adnexal epithelium is seen. Objective: Our aim was to describe the clinical features of DEPS. Methods: We undertook a retrospective case series of 13 patients with DEPS. Results: All 13 patients were fair-skinned men older than 50 years with a history of significant sun exposure. The lesions were present on the scalp, face, and neck. Histologic examination showed a growth of atypical keratinocytes in the lower epidermis with encasement of adnexal structures by atypical neoplastic keratinocytes. In the 52 cumulative patient-years of follow-up, we treated 80 invasive squamous cell and 48 basal cell carcinomas in these patients. Despite improvement of DEPS with aggressive topical and destructive therapy, multifocal recurrence would typically develop within a few months. Conclusion: DEPS is characterized by diffuse involvement of chronically sun-exposed skin with atypical keratinocytes that grow along the inferior portion of the basal layer of the epidermis and around adnexal structures. The treatment of DEPS is challenging because of its widespread nature and deeper periadnexal involvement. DEPS is also associated with the development of invasive squamous cell and basal cell carcinomas.
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