Perianal Paget disease. Histochemical differentiation utilizing the borohydride-KOH-PAS reaction.

Specimens from various types of Paget disease, other tumors, and certain normal tissues were examined with a battery of histochemical techniques, including the sodium borohydride-potassium hydroxide-PAS method that specifically stains certain sialomucins that are found in terminal parts of the ileum and of the colon. These sialomucins were present in normal anal ducts but were not present in transitional or anal-covering epithelium. A case of perianal Paget disease showed strongly positive staining, both in the underlying mucinous adenocarcinoma and in Paget cells of the affected anal and perianal skin. In contrast, stains of other forms of Paget disease were totally negative with this technique, as well as malignant melanoma and Bowen disease. These results support the theory that Paget disease represents epidermal invasion by malignant cells from underlying tumor.