Immunohistochemical Expression of p21 in Ductal Carcinoma of the Breast and its Correlation with HER2/neu Expression and Hormonal Status

Breast cancer is the most common malignancy affecting women.It accounts for 23% of all cancers in women all over the world. In Egypt, breast cancer is the most common cancer among Egyptian women. Inspite of the improvements in early diagnostic methods of breast cancer and also the advances in treatment, mortality rate because of the disease remains high. The cyclin-dependant kinase inhibitor p21 (WAF1/CIP1) is a key regulator of progression from the G1 to the S-phase of cell cycle. This work aimed at studying the expression of p21 in invasive carcinoma of the breast in correlation with well-established prognostic factors in breast cancer including estrogen receptor, progesterone receptor status and HER2/neu expression. This study was carried out by retrieval of formalin-fixed, paraffin-embedded tissue sections from archival blocks prepared from 60 modified radical mastectomy specimens diagnosed as invasive duct carcinoma of the breast.The specimens were collected from the Department of Pathology, Kasr Al Aini Hospital School, Cairo University, Egypt from January 2011 till December 2012. Each case was tested for immunohistochemical expression of p21, estrogen receptors, progesterone receptors and HER2/neu. P21 expression was correlated significantly with the microscopic grade. Also, a highly significant relationship was found between p21 and expression of estrogen and progesterone receptors; moreover, loss of p21 was associated with positivity to HER2/neu. Our findings strongly suggest that p21 (WAF1/CIP1) expression may be used as a potential prognostic marker for human breast cancer, allowing therapy to be adjusted more appropriately for individual tumors.