Expression of S100 protein family members in normal skin and sweat gland tumors

Background Despite our growing knowledge regarding the biology of S100 family proteins in cancers and internal diseases, limited data are available with their distribution in normal skin and in sweat gland tumors. Objective To study the expression and distribution pattern of multiple S100 proteins in normal skin and in the tumors of sweat glands. Methods Immunohistological staining was performed using S100A2, S100A4, S100A6, S100A7, S100A8/9, S100A11, and S100P in 41 cases of various kinds of sweat gland tumors and in 13 cases of normal skin. Results In normal skin, S100A2, S100A6, S100A7, and S100P staining were observed in the sweat glands. S100A2 positively stained in the outer layer of the eccrine duct. S100A6 immunolabeling was observed in the secretory portion of the eccrine gland. Myoepithelial cells of the apocrine gland were positive for S100A2 and S100A6. S100A7 was positive in the acrosyringium, ductal, and secretory portions of the eccrine gland and in the inner layer of the apocrine gland. Intense S100P staining was detected in the inner layer of the acrosyringium and eccrine ducts. Langerhans cells and melanocytes showed strong immunoreactivity to S100A4. Extramammary Paget's disease (EMPD) expressed S100A7 and S100P with partial S100A6 and S1004 staining. Eccrine poroma expressed S100A2 and S100A7 with partial labeling with S100A6. Syringoma expressed S100A2, S1007, and S100P. Apocrine hidrocystoma expressed S100A2 with partial S100A6 and S100A7 immunoreactivity. Syringocystadenoma papilliferum expressed S100A2, S100A6, S100A7, and S100P. Conclusion S100A2, S100A6, S100A7, and S100P proteins are specifically involved in structure-related distribution and are potentially useful for differential diagnoses of sweat gland tumors.