Pagetoid dyskeratosis of the prepuce. An incidental histologic finding resembling extramammary Paget's disease

Background: Pale cells resembling those of paget's disease have been seen a s an incidental finding within tilt, epidermis in a variety of benign papul es most commonly located in intertriginous areas. This lesion, called paget oid dyskeratosis, is considered a reactive process in which a small part of the normal population of keratinocytes is induced to proliferate. Among th e inductors friction is suspected. As far as we know, these cells have not been reported in the penis. Methods: Here we describe the location of the lesion in the foreskin and th e incidence of this lesion in a group of 281 unselected patiets surgically treated for phimosis. In selected cases histochemical staining and immunohi stochemical studies were performed. Results: Pagetoid dyskeratosis was found in 105 cases (37.4%) bur only in 5 cases (1.8%) the lesion was conspicuous. The cells of pagetoid dyskeratosi s show an immunohistochemical profile different from the surrounding kerati nocytes characterized by premature keratinization. Pagetoid dyskeratosis ce lls must be distinguished from the artefactual clear cells of the epidermis , from reactive melanocytes, and from pale-cell acanthosis. In cases in whi ch pagetoid dyskeratosis shows a florid expression there is a hazard of ove rdiagnosis to the patient. The main differential diagnosis includes extrama mmary Paget's disease, pagetoid squamous cell carcinoma in situ, epidermotr opic metastasis, superficial spreading malignant melanoma, clear cell papul osis, and penile koilocytoses. Conclusions: The pathologist should be familiar with the histologic feature s of pagetoid dyskeratosis in the foreskin in order to avoid misdiagnosis a nd unnecessary treatment. Routine histologic study is usually sufficient to identify the lesion.