Immunohistochemical characterization of non‐epithelial cells in spiradenoma

Spiradenoma is unique with respect to the presence of a large number of non-epithelial cells, including S100 protein+ cells, most of which are presumably Langerhans cells, in the parenchyma as shown in the published work. However, the characterization of these non-epithelial cells to date is insufficient. Immunohistochemistry of CD1a, CD3, CD4, CD8, CD56, CD68, intercellular adhesion molecule-1 (ICAM-1), and HLA-DR, as well as double-immunofluorescence labeling of S100 protein/CD1a and CD1a/CD3, was performed using paraffin-embedded specimens from five cases of spiradenoma retrospectively. Non-epithelial cells evenly distributed throughout the parenchyma of spiradenoma primarily consisted of CD1a+ Langerhans cells and CD3+ T cells. ICAM-1 was expressed by epithelial cells and non-epithelial cells in the parenchyma. HLA-DR on the epithelial cells was limited to the focal area. In double-immunofluorescence labeling, approximately one-half of Langerhans cells were spatially related to T cells in the parenchyma, suggesting their functional interaction.