Immunohistochemical Study of Non-Epithelial Cells in Spiradenoma

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Background: Intratumoral lymphocytes are a defining feature of spiradenoma; however, there have only been a few reports on the phenotypic features of non-epithelial cells. Spiradenomas also contain numerous cells positive for S-100 protein and the nature of these cells is still controversial. Methods: We performed a clinicopathological and immunohistochemical study of ten cases of spiradenoma. Results: The study included seven men and three women. On histopathological examination, spiradenoma could be divided into two types: the vascular proliferating (VP) type (five cases) that featured granulation tissue with edema, vascular proliferation, and inflammatory cell infiltration into the stroma, and the common type (five cases), which did not include any of the aforementioned features. Immunohistochemical staining demonstrated a large number of cells positive for S-100 protein. These included cells with large pale nuclei, dendritic cells, and a few cells with small dark nuclei that were also positive for α-smooth muscle actin. Most of the cells infiltrating the parenchymata of these lesions were CD3-positive. The proportions of CD4-positive and CD8-positive cells were almost equal or CD8-positive cells were predominant. CD20+ cells were observed in five spiradenomas. In painful lesions, there were numerous nerve fibers near the tumor. Conclusions: In spiradenoma, CD3+ T cells were mainly seen in the parenchyma and CD8+ cells were predominant over CD4+ cells in most cases. CD20+ cells showed focal infiltration of the parenchyma and stroma, especially in VP-type lesions. S-100 protein-positive cells in spiradenoma contained not only Langerhans cells, but also cells with myoepithelial differentiation.