| • | ddx: psoriasis, chronic eczema (including tinea), superficial BCC, seborrheic keratosis |  
 | • | histology:  atypical cells throughout entire thickness of epidermis, and involve epidermal appendages, especially hair follicles (vs. AK) |  
 | • | classic immunohistochemistry panel:  Paget’s vs. superficial spreading melanoma vs. Bowen's (see EMPD for detailed immunohistochemistry) |  
   
| • | appears exclusively under the foreskin of the uncircumcised penis |  
 | • | treatment of choice = 5-FU cream vs. aldara |  
 | • | recurrences are unlikely because hair follicles that serve as foci for recurrence are absent on the penile mucosa |  
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