We have evaluated HER2/neu expression in 1,355 breast cancer patients recruited at the Breast Cancer Registry in Palermo between January 1999 and December 2004. In this retrospective study, HER2/neu expression was related to clinicopathologic features of the disease, including tumor size, nodal and menopausal status, estrogen and progesterone receptors. Statistical analysis on all 1,355 patients showed a significant correlation between HER2/neu and nodal status (P < 0.001), and a significant association between HER2/neu overexpression and estrogen and progesterone receptors status (P < 0.001). In 194 patients without metastasis, with an average follow-up > or =5 years, only HER2/neu 3+ and histopathologic grading G3 were significantly associated with overall survival.