Atypical Lobular Hyperplasia of the Breast
Differential Diagnosis
- Lobular carcinoma in situ vs. atypical lobular hyperplasia
- Normal acini vs. atypical lobular hyperplasia
- Ductal carcinoma in situ vs. atypical lobular hyperplasia
LCIS vs. Atypical Lobular Hyperplasia (ALH)
- LCIS requires that all the acini in at least one lobular unit be completely filled and that half the acini in that unit must be expanded
- If either of the above features is lacking, designate as ALH
Normal Breast Acini vs. Atypical Lobular Hyperplasia (ALH)
- ALH requires at least one of the following features:
- At least one acinus must be filled by characteristic lobular cells, OR
- Characteristic lobular cells must be present beneath normal acinar cells in several acini of a lobule
- There is no category of (non-atypical) lobular hyperplasia
Ductal vs. Lobular differentiation may be a problem in pagetoid or complete involvement of ducts by ALH or in lobular involvement by DCIS cells (cancerization of lobules)
| DCIS | ALH |
|---|---|
| Cohesive | Non-cohesive |
| May show moderate to marked pleomorphism | Mild to moderate pleomorphism |
| No pagetoid involvement of ducts | May show pagetoid pattern in ducts |
| Frequent intraductal cribriform or micropapillary pattern | No cribriform spaces or micropapillae |
| E-cadherin positive | E-cadherin negative |
