This is a solitary lesion on the dorsum of the right hand of a 45-year-old woman. This is a good example of how squamous cell carinoma in situ (Bowen's disease) can have a pagetoid appearance. The differential diagnosis for lesions with this pagetoid look includes melanoma in situ, Paget's disease, and epidermal involvement of an adnexal carcinoma, such as sebaceous carcinoma. Immunohistochemical analysis can help with difficult cases.
Immunohistochemical analysis demonstrates positive staining for cytokeratins (AE1/3). Carcinoembryonic antigen (CEA) nicely highlights an acrosyringium, but is negative within the lesion. S100 only stains junctional melanocytes and interspersed Langerhans cells.