The significance of combined CK5/6 and p63 immunohistochemistry in predicting the risks of subsequent carcinoma development in intraductal papilloma of the breast.

Prediction of subsequent risks of breast carcinoma (BC) development in intraductal papilloma (IDP) has remained controversial with the exception of atypical papilloma (AP). The potential value of immunohistochemistry (IHC) of cytokeratin 5/6 [CK5/6] and p63 have been proposed but its standardization has also remained controversial. We studied 17 patients initially diagnosed as IDP or AP who subsequently developed BC with 34 age-matched controls. We compared histological features, results of IHC (estrogen receptor [ER], progesterone receptor [PR], human epidermal growth factor receptor 2 [HER2], p63, CK5/6, Ki67), and ultrasound findings. Univariate conditional logistic regression analysis revealed that the status of both CK5/6 and p63/CK5/6 were significantly associated with subsequent BC development (P < 0.05). BC development in CK5/6 positive patients was 17.9% and p63/CK5/6 double positive patients 8.6%, respectively. Ultrasound evaluation was not significantly associated with any of the parameters examined and subsequent carcinoma development. Despite CK5/6 positivity, the subsequent incidence of BC development was nearly 20%. However p63/CK5/6 double positive status could predict a significantly lower subsequent carcinoma incidence, indicating a more accurate prognostic utility. Combining p63/CK5/6 with histological findings could be easily applied and could predict the subsequent BC development of the patients diagnosed as IDP at biopsy.