Simple Breast Cysts

Fibrocystic Change - Cystosis

• Cyst = Fluid filled cavity lined by epithelial cells
• Cystic involution of the breast lobule (Apocrine)
  • Outflow obstruction due to epithelial hyperplasia / stricture or fibrosis of terminal ductules / kinking of ducts + secretion by distal lobule → Cyst
  • Lobules develop microcysts → coalesce into larger cysts
• Characteristic halos on mammography
  • USS essential
    • Can distinguish solid and cystic lesions
    • Also give info on septations and differentiate simple and complex cysts
• Simple Breast Cysts
  • No association with cancer
  • Lined by simple cuboidal epithelium
  • Classic USS features meaning likely benign
    • Wall calcified
    • Mobile particles (usually cholesterol crystals)
• Complex Breast Cysts
  • Possible association with cancer
  • Lined by apocrine epithelium (apocrine metaplasia) with columnar cells
  • High K:Na ratio
  • Tend to recur

Cancer risk ↑ed (estimated >2%) if:

• Blood in cyst
• Lump present after aspiration
• Thickened walls
• Thick (> 2mm) internal septations
• Mix of cystic & solid components
• Co-existent Florid ductal hyperplasia

Northshore Guidline