[292] Yes-Associated Protein (YAP) Is Expressed in a Subset of Triple-Negative Breast Cancers.

Saba Yasir, Rozina Tufail, Carmen Gomez-Fernandez, Zafar Nawaz, Prodipto Pal, Merce Jorda. University of Miami, Jackson Memorial Hospital, FL; University of Miami, FL

Background: Breast cancer is a heterogenous disease comprising several molecular and morphological entities with distinct prognostic and therapeutic differences. It is critical to identify novel markers for distinguishing these subgroups. Here we report the immunohistochemical utility of YAP, a gene involved in several aspects of breast cancer signaling. YAP is a co-activator of estrogen (ER) and progesterone (PR) receptors.
Design: We randomly selected 54 cases of breast carcinoma obtained between 2007 and 2009. Cases were divided into 3 groups based on estrogen and progesterone receptor status and HER2 immunoreactivity and into 2 groups based on morphologic characteristics: glandular/tubular and solid/syncytial. The glandular/tubular group was characterized by glandular/tubular structures with scores 1 to 3 of Nottingham scoring system. The solid/syncytial group was characterized by sheets of malignant cells without glandular/tubular structures. All cases including 10 breast control samples were stained using YAP antibody. Nuclear immunoreactivity was considered positive. Chi-squared and Fisher tests were used for statistical analysis.
Results: Twenty-four (44%) cases were negative for ER, PR and HER2 (triple negative tumors). Of those, 14 (63%) were negative and 9 (37%) were positive for YAP; twenty-three (43%) cases were positive for ER and PR and negative for HER2. Of these, 14 (61%) were positive and 9 (39%) were negative for YAP; seven cases (13%) were HER2 positive (5 triple positive and 2 were negative for ER and PR). Of these, 4 (57%) were positive and 3 (43%) were negative for YAP. When the cases were evaluated by morphologic characteristics, 39 (73%) were classified as glandular/tubular of which 26 (67%) were positive and 13 (33%) were negative for YAP. Fifteen (27%) cases were classified as solid/syncytial, of which 14 (93%) were negative and only 1 case (7%) expressed YAP. A positive correlation was observed between glandular/tubular morphology and immunoreactivity for YAP independent of hormone status and HER2 expression (p<0.0001).
Conclusions: 1- YAP is more frequently expressed in ER/PR positive breast tumors; 2- Approximately two-thirds of ER/PR positive tumors expressed YAP; 3- Approximately one-third of triple negative tumors expressed YAP; 3- YAP positive triple negative tumors demonstrate glandular/tubular morphology; 4- Triple negative tumors with a glandular/tubular morphology may share molecular characteristics with ER/PR positive tumors.
Category: Breast

Monday, February 28, 2011 1:00 PM

Poster Session II # 75, Monday Afternoon


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