Fig. 1. Normal structure of the mammary gland. A: Radial US scan shows normal lobules (arrowhead) and ducts extending from the nipple to the periphery as hypoechoic tubular structures. Two parallel hyperechoic lines (arrow) within the structure are due to US reflections from the mammary duct wall. B: Histopathology (hematoxylin and eosin stain) obtained from a different patient shows normal mammary ducts (arrow), lobules (arrowheads), and fibrous and adipose stroma. US = ultrasound.