Ductal Adenoma of the Breast

Definition

Circumscribed breast mass with a prominent fibrotic capsule and a bilayered tubular component

Combines morphologic features of sclerosing adenosis and papilloma
Circumscribed, encapsulated
- Surrounded by fibrous capsule
- Single or multiple nodules
  - May be discrete or in continuity within a ductal system
Prominent hyalinizing fibrosis
- Frequently denser in center
- May form stellate scar but periphery still circumscribed
- Lacks papillary structure
Intermixed bland ducts
- Lined by epithelial and myoepithelial layers
- Peripheral ducts frequently dilated
- Central ducts may be compressed or obliterated
- Apocrine metaplasia frequent
  - Nuclei and nucleoli may be enlarged in apocrine areas
- Apical snouts may be prominent
- Lumenal calicification may be present
May demonstrate myoepithelial overgrowth
Peripiheral lymphoid infiltrate may be present

Richard L Kempson MD
Robert V Rouse MD
Department of Pathology
Stanford University School of Medicine
Stanford CA 94305-5342