Micropapillary breast carcinoma is a rare variant.
Micropapillary carcinoma of breast has a few unique clinical, microscopic and immunological features which aid in their differentiation from other subtypes of breast carcinoma.
Let’s look at them!!
1. Tufts of cells arranged in pseudopapillae ( lack fibrovascular cores). These pseudopapillae are surrounded by empty clear spaces formed by fibrocollagenous stroma.
2. Aggressive tumor usually present with angiolymphatic invasion. They present with nodal invasion at the time of presentation.
3. Molecular and cytogenetics: BC-1514 (C21orf118) is commonly upregulated in the micropapillary area.
4. ER positive in 90% and PR positive in 50%
5. Micropapillary breast carcinomas show
‘INSIDE OUT’ staining pattern with EMA and CD15s.
INSIDE OUT staining pattern refers to – staining localized to the apical surface of tumor cells abutting the stroma but absent staining in the basolateral region.
6. Another characteristic of micropapillary breast carcinoma is Incomplete basolateral or CUP SHAPED staining with apical sparing seen with E- cadherin, Her-2-neu and p-120.
Below is a picture which will help you remember all characteristics of micropapillary breast carcinoma.