RESUMEN
<p><b>OBJECTIVE</b>To study the expression of phosphatase and tensin homology deleted on chromosometen ten (PTEN) protein, a tumor suppressor gene in breast cancer and its correlation with p27(kip1) and cyclin D1 expression.</p><p><b>METHODS</b>PTEN protein expression, p27(kip1) and cyclin D1 protein expression were detected by immunohistochemical method in paraffin sections from 61 women with primary breast cancer. PTEN protein expression was compared with clinico-pathologic parameters as related to p27(kip1) and cyclin D1.</p><p><b>RESULTS</b>PTEN, being shown in the cytoplasm, was negative in 6.6% (4/61), reduced in 41.0% (25/61) and positive in 52.5% (32/61) samples. PTEN expression level was correlated with axillary lymph node status, loss of estrogen receptor stain, recurrence and metastasis. On univariate analysis, the disease-free survival rate of patients with higher PTEN expression (> 50% cells stained) was better than those with lower expression (P = 0.0101). However, there was no correlation between p27(kip1), cyclin D1 expression or PTEN expression.</p><p><b>CONCLUSION</b>PTEN, its lower expression being correlated with poor outcome of breast cancer patients, plays a prominent role in breast cancer. p27(kip1) or cyclin D1 may not be the primary downstream genes of PTEN in breast cancer.</p>