Expression of Stem-Cell Markers (Cytokeratin 15 and Nestin) in Primary Adnexal Neoplasms-Clues to Etiopathogenesis

Background: The overlap in histopathologic features and immunoprofile of eccrine and apocrine neoplasms confounds basic issues relating to lineage of these entities. Methods: We evaluated expression of follicular stem-cell markers, cytokeratin (CK) 15 and nestin, in 78 benign and 23 malignant adnexal neoplasms. Results: CK15 and nestin expression were noted in 39 of 78 (50%) and 36 of 78 (46%) cases in the benign group, respectively (8 cutaneous mixed tumor, 10 hidradenoma papilliferum, 9 apocrine cystadenoma, 11 cylindroma and/or spiradenoma, and 9 poroma/dermal duct tumor). CK15 and nestin expression were noted in 11 of 23 (48%) and 7 of 23 (30%) cases in the malignant group, respectively (6 microcystic adnexal carcinoma, 7 porocarcinoma, and 9 eccrine carcinoma). Except 1, both markers were negative in 4 syringocystadenoma papilliferum, 10 hidradenoma, 1 syringofibroadenoma, 10 syringoma, 1 eccrine adenoma, 8 poroma/dermal duct tumor, 5 eccrine hidrocystoma, and 1 apocrine carcinoma. Conclusions: Given that follicular germinative cells give rise to the folliculosebaceous apocrine unit, expression of CK15 and nestin in the majority of cutaneous mixed tumor, hidradenoma papilliferum, apocrine cystadenoma, and cylindroma/spiradenoma is suggestive of an apocrine origin/differentiation of these neoplasms. Reinforcing this and a novel finding of our study is the preferential expression of nestin in myoepithelial cells of these lesions.