Adenomyoepithelioma of the breast

Adenomyoepithelioma of the breast is a rare lesion characterized by biphasic proliferation of ductal epithelium and myoepithelial cells. A 37-year-old female presented with a non-tender, mobile, smooth mass located in the retroareolar area of her left breast. Ultrasonography revealed a 1.76 × 1.73 × 1.23 cm wider-than-tall tumor with homogeneous hypoechoic echotexture. The tumor margins were smooth with a thin echogenic capsule. The tumor was compressible and had posterior acoustic enhancement. Histopathologic analysis demonstrated a well-circumscribed tumor with mammary ductal epithelium and myoepithelium in the fibrous stroma. Immunohistochemical staining was positive for smooth muscle actin, vimentin, and S-100 protein in the myoepithelial cells. No recurrence or distant metastases was observed during a 14-month follow-up period.