Mucin-negative biopsy in extra-mammary Paget's disease. A diagnostic problem.

A case of extra-mammary Paget's disease with a mucin-negative small biopsy is reported. Study of a small series of vulvar Paget's disease demonstrated that areas devoid of mucin in the mm range are frequently found, creating the conditions for diagnostic problems in small biopsies. In this situation, positive immunoreactions for carcinoembryonic antigen and low molecular weight cytokeratins and a negative reaction for S-100 protein serves to differentiate Paget's disease from other pagetoid lesions.