Chromosomal 7 and 17 Polysomy in Triple Negative Invasive Breast Carcinoma.
Claudia Velosa, Patrick Storto, Jan F Silverman, Uma Krishnamurti. West Penn Hospital, Pittsburgh, PA; Allegheny General Hospital, Pittsburgh, PA
Background: Breast cancer is a heterogeneous malignancy encompassing several entities that have distinct morphologic features as well as clinical behavior. We have previously evaluated the adverse significance of unamplified polysomy 17 in invasive breast carcinomas (IBC). Triple negative IBC are those that lack ER, PR, and HER2 expression, a subset of which are basal like. The aim of this study was to evaluate triple negative IBC for HER1 and HER2 amplification and chromosomal 7 and 17 status.
Design: 45 cases of triple negative IBC (lacking ER, PR, and HER2 expression by IHC) from 2005 to 2010 were selected. IHC stains for cytokeratin 5/6 (CK5/6) and EGFR were performed in all cases. Triple negative IBC that were CK 5/6 positive and/or EGFR positive were considered to be of basal type. FISH for HER1 and HER2 amplification was performed on 11 cases of basal type and 6 cases of non-basal type triple negative IBC. Polysomy was defined as the presence of >3.0 centromere copies/cell and HER1 or HER2 amplification was defined by HER1/CEP7 or HER2/CEP17 copy ratio >2.2.
Results: Of the 45 triple negative IBC, 13 cases (29.0%) were of basal type. 5 cases were positive for EGFR and CK 5/6 by IHC. Table 1 shows the mean of HER1, CEP7, HER2, and CEP17 copy numbers. Amplification of HER1 or HER2 was not detected in any of the cases. Higher mean HER1 and CEP7 copy numbers were seen in basal type triple negative IBC compared to the non-basal type, although the differences were not statistically significant. Polysomy 7 was present in 59.0% of all triple negative IBC, in 8 of 11 (72.7%) of basal type and in 2 of 6 (33.0%) of non-basal type triple negative IBC. Polysomy 17 was seen in 3 of 11 (27.7%) of basal type IBC. Polysomy 17 was not detected in any non -basal type triple negative IBC.
|HER1 Copy/Cell Mean+- SEM||CEP7 Copy/Cell Mean+- SEM||HER2 Copy/Cell Mean+- SEM||CEP17 Copy/Cell Mean+- SEM|
|Basal Type (CK5/6+)||4.4+- 3.0||4.2+- 6.6||2.6 +- 0. 9||2.6 +- 0.8|
|Non-basal Type (CK5/6-)||2.5 +- 0.7||2.4 +- 0.7||2.1 +- 0.6||1.9 +- 0.5|