Infiltrating Ductal Carcinoma of the Breast (Carcinoma of No Special Type)

Minimal Stromal Invasion

Extension of cancer cells beyond the basment membrane into the adjacent tissue with no focus more than 0.1 cm in greatest dimension (AJCC T1mic)

Multiple foci are not added together for evaluation of the size criterion
Calponin and p63 stains can be useful
Focus should be outside the lobular unit or immediate periductal area
- If cells are present in these areas, designate as "scattered cells in perilobular or periductal area"
  - Note in report that they do not meet the criteria for minimal stromal invasion
  - Note that their clinical significance is unknown
Significance
- Less than 5% chance of metastases
- Nearly 100% survival
If this is the only invasion present, we report it as DCIS with minimal stromal invasion
- We avoid the term "microinvasion" because of its varying definitions