Abstract: XUE Yan-ning*, CHEN Hao, SUN Qi, LI Yang, ZONG Wen-kai, SUN Jian-fang. *Department of Dermatology, Jiangsu Provincial Hospital of Traditional Chinese Medicine, Nanjing 210029, China Corresponding author: CHEN Hao, Email: ch76ch@163.com 【Abstract】 Objective To study the clinicopathological features of syringomatous adenoma of the nipple （SAN）. Methods The clinical, histopathological and immunohistochemical findings of four cases of SAN were described, with a review of the literature. The diagnosis and differential diagnosis of SAN were also discussed. Results Among the four patients, three were female, and one was male. The mean age at onset was 42 years, and clinical course ranged from 3 months to 10 years. Clinically, SAN was manifested as an asymptomatic subcutaneous nodule, which was located in the areola of breast of female patients and in the right armpit of the male patient. Histopathologically, the tumor was located in the dermis and subcutaneous tissue, composed of nests and cords of epithelial cells forming tubular structures and infiltrating the indurated stroma between smooth muscle bundles. These tubules were lined by two layers of cells and displayed a "comma" or "tadpole" shape. Keratotic microcysts were seen. Immunohistochemically, the tumor cells stained positive for cytokeratin, cytokeratin 5/6, Ki67 （1%）, but negative for estrogen receptor, progesterone receptor, CerbB2, cytokeratin 8/18, P53 and gross cystic disease fluid protein-15 （GCDFP-15）. The peritubular myoepithelial cells expressed P63 and smooth muscle actin （SMA）. Conclusions SAN is a rare benign tumor, which is often confused with some benign and malignant carcinomas of the breast.

Key words: syringomatous adenoma