Ductal Carcinoma in Situ of the Breast

Variant: Papillary Ductal Carcinoma In Situ

Large dilated duct or cystic space
Four main patterns
- Cribriform DCIS
  - Resembles ordinary cribriform DCIS on papillary stalks
  - May arise in a papilloma
    - If <3 mm or involves <30% of papilloma, diagnose as atypical ductal hyperplasia
  - Myoepithelial cells should not be present in cribriform areas but may be present along stalks
- Tall hyperchromatic or stratified spindle cell
  - Lined by single population of tall cells
  - Elongate hyperchromatic stratified or pseudostratified nuclei perpendicular to stalk
  - Complex arborizing thin, delicate fibrovascular stalks
  - Myoepithelial cells are not typically present on the stalks
  - May have nuclear clearing
- Compact columnar
  - Lined by uniform population of often columnar cells
  - Fine, evenly distributed chromatin
- Transitional cell
  - Resembles low grade transitional cell carcinoma
High grade cytology rare
Mitotic figures may be seen
- They are rare in papillomas over age 40
Necrosis may be seen
- It is rare in papillomas over age 40
Myoepithelial cells often cannot be demonstrated around the outside of papillary DCIS; however, papillary DCIS is not clinically an invasive carcinoma
Invasion, when it occurs, is typically low grade infiltrating ductal or very rarely invasive papillary