This skin biopsy shows extensive dermal solar elastosis consistent with sun (actinic) damage. In the epidermis is a neoplastic proliferation of atypical, enlarged squamous epithelial cells. The process is confined to the epithelium, consistent with squamous cell carcinoma in situ (Bowen's disease). Grossly it is an erythematous, velvety, slightly raised plaque. Less than 2% of these lesions are pigmented, as in this case. The major differential diagnosis here is lentigo maligna in which large polygonal atypical melanocytes appear mainly at the dermal-epidermal junction. An increase in skin cancers in the latter part of the 20th century was, in part, attributable to environmental degradation via increasing halocarbon (including chlorofluorocarbon) emissions that depleted the earth's stratospheric ozone layer. The 1985 Vienna Convention provided the framework for international restrictions on the production of ozone-depleting substances.