[158] A Comparative Study of p16 Expression in Basal-Like Carcinoma and High-Grade Invasive Ductal Carcinoma of the Breast

OL Bohn, M Fuertes-Camilo, L Navarro, J Saldivar, S Sanchez-Sosa. Christus Muguerza UPAEP University Hospital/Hospital Angeles, Puebla, Mexico

Background: Basal-like carcinomas of the breast (BLCB) are one of the molecular subtypes determined by gene expression profiling. BLCB generally have a high mitotic index, are ER-/PR-/HER2- (“triple-negative breast cancer”), and show variable expression of CK 5/6, CK14, EGFR and CD117. p16INK4a expression has been identified in HPV-related carcinomas of genital tract and oropharynx. Little is known about p16INK4a and BLCB. The aim of this study was to determine p16INK4a expression in a subset of BLCB and compare the results with a group of high-grade invasive ductal carcinoma (HG-IDC) of breast.
Design: Tissue microarrays (TMA) were constructed in triplicate including 18 HG-IDC and 18 BLCB. Whole tissue sections were also used for BLCB. Immunohistochemical (IHC) stains for ER, PR, HER2, CK5/6, CK14, EGFR, CD117 and p16 were performed. The slides were stained using DAKO autostainer. Positive and negative controls were applied.
Results: The IHC results are summarized in Table 1.

p16Positive16 (89%)10 (55.5%)
Negative2 (11%)8 (44.5%)
CK5/6Positive17 (94.4%)5 (28%)
Negative1 (5.6%)13 (72%)
CK14Positive17 (94.4%)3 (17%)
Negative1 (5.6%)15 (83%)
EGFRPositive14 (78%)2 (11%)
Negative4 (22%)16 (89%)
CD117Positive13 (72%)2 (11%)
Negative5 (28%)16 (89%)
ERPositive0 (0%)2 (11%)
Negative18 (100%)16 (89%)
PRPositive0 (0%)3 (17%)
Negative18 (100%)15 (83%)
HER2Positive0 (0%)3 (17%)
Negative18 (100%)15 (83%)

All BLCB cases were ER-/PR-/HER2-. Seventeen BLCB were CK 5/6+/CK 14+; EGFR was positive in 14/18 BLCB and CD117 was expressed in 13/18 BLCB. Nuclear diffuse expression of p16INK4a was seen in 16/18 (89%) BLCB, ranging from 80% to 100%; nuclear p16INK4a staining was present in 10/18 (55.5%) HG-IDC, ranging from 5% to 100%.
Conclusions: Our study shows that p16INK4a was highly expressed in the majority of BLCB (89%) in comparison to HG-IDC (55.5%). In triple-negative breast cancer cases with CK5/6 and CK14 co-expression, p16INK4a may serve as an additional biomarker for identification of BLCB.
Category: Breast

Monday, March 22, 2010 1:00 PM

Poster Session II # 66, Monday Afternoon


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