['To investigate the impact of lack of progesterone receptor (PR) expression on the prognosis of patients with operable ER (estrogen receptor)-positive invasive breast cancer.', 'We retrospectively analyzed the clinicopathological features, treatment and survival data of 318 women with ER+ /PR+ and ER+ /PR- invasive breast cancer.', 'Among the 318 patients, there were 219 PR-positive and 99 PR-negative cases. The 5-year overall survival (OS) rate was 92.5%, and the 5-year disease-free survival (DFS) rate was 87.2% in the 318 ER-positive patients. Among them, the 5-year OS rates were significantly different between the PR-positive group (94.6%) and PR-negative group (87.8%, P=0.020), and the 5-year DFS rates were also significantly different from each other (89.8% and 81.6%, respectively, P=0.019). Univariate analysis showed that PR status, tumor size, T stage, axillary lymph node metastasis, and clinical stage were prognostic factors for OS (P<0.05 for all). Multivariate analysis showed that lack of PR expression, T stage ≥2, and positive axillary lymph node metastasis were independent risk factors for poor DFS and OS in ER-positive breast cancer patients (P<0.05 for all). Subgroup analysis showed that lack of PR expression was not significant in predicting poor DFS or OS when patients were in stage Ⅰ or with a small tumor (≤2 cm) (P>0.05 for all), and also showed that premenopausal women with PR-negative disease had poorer DFS and OS than PR-positive patients (P<0.05 for both).'] Does [ Lack of progesterone receptor expression predict poor prognosis in patients with operable ER-positive invasive breast cancer ]?