Two cases of vulval pigmented extramammary Paget's disease: histochemical and immunohistochemical studies.

We describe two Japanese female patients with pigmented extramammary Paget's disease (EMPD); one patient had a dark brown plaque and the other had a reddish patch with a pigmented area, both affecting the vulval region. Histochemical and immunohistochemical examinations confirmed EMPD with melanocyte colonization; plump tumour cells with a large nucleus and pale cytoplasm that were positive for CAM 5.2 and CEA proliferated singly or in nests in the epidermis, and scattered among the tumour cells were many dendritic cells with a large amount of melanin that were positive for HMB-45 and S-100 protein. Fontana-Masson (FM) stain showed many positive cells with well-developed dendritic processes within and around tumour nests. Histochemical and immunohistochemical studies of non-pigmented EMPD cases on the same region showed that HMB-45 positive cells were sparse or not detected at all, and that also FM staining-positive cells were decreased or not detected, and their dendritic processes were poorly formed. The present study suggests that there might be heterogeneity in EMPD in terms of relationships between Paget's cells and melanocytes.