The patient is a 67-yr-old woman with who presented with an erythematous, scaly plaque on her vulva that she described as being intensely pruritic. On clinical examination, the lesion appeared erythematous and slightly hyperpigmented. The clinical differential diagnosis included extra-mammary Paget's disease, squamous cell carcinoma in situ, seborrheic dermatitis, intertrigo, and candidiasis.
A small punch biopsy was performed and yielded the following specimen as seen in Fig. 1A,B.
While the clinical presentation was most in keeping with a diagnosis of extramammary Paget's disease, the histology was difficult to interpret and a differential diagnosis was generated. In order to resolve the diagnostic dilemma, a strategy for immunolabeling tissue sections was developed and is presented in Table 1.
The staining pattern is depicted in Fig. 2A-C. As can be seen, there is strong staining of the large, atypical cells with cytokeratin 7 and epithelial membrane antigen. The staining with AE1/AE3 is somewhat difficult to interpret and there is no staining with S100. The negative
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