Background
Focal adhesion kinase (FAK) is an enzyme of the tyrosine kinase group linked to signaling pathways between cells and the extracellular matrix. In tumor cells in vitro, FAK expression correlated with their ability for invasion and metastasis. Additionally, in vivo FAK has been implicated in malignant transformation and disease progression. The aim of the present study was to evaluate the clinical significance of FAK expression in breast ductal invasive carcinoma (DIC).
Material and Method
Immunocytochemical techniques were used to assess FAK expression on cytological material obtained from 73 patients with breast DIC. FAK expression status (positivity, overexpression, and intensity of immunostaining) was compared with clinicopathological parameters and the tumor cells' proliferative capacity.
Results
Sixty-four of the 73 DIC cases (88%) were FAK positive and FAK protein overexpression was noted in 15 of the 73 (21%). In the DIC cases examined, FAK positivity correlated with tumor size (p=0.016) and FAK protein overexpression with tumor histological grade (p=0.034) and the tumor cells' proliferative capacity (p=0.003). The intensity of FAK protein staining did not significantly correlate with any of the examined clinicopathological parameters.
Conclusions
In breast DIC it becomes evident that FAK protein positivity and overexpression correlate with important clinicopathological parameters. Further molecular and clinical studies are required to delineate the significance of FAK as a factor for better prognosis and management of breast cancer patients.

Keywords: Focal Adhesion Protein-Tyrosine Kinases - metabolism, Cytoplasm - pathology, Carcinoma, Ductal, Breast - pathology, Breast Neoplasms - pathology, Aged, 80 and over