Background: Patients whose tumors express only one hormone receptor (1HR) are usually considered hormone-sensitive regarding treatment decisions. However, certain retrospective analyses suggest that patients bearing ER+/PR- or ER-/PR+ tumors may have worse outcomes than those with ER+/PR+ (HR) phenotype. The aim of this study was to correlate partial expression of hormone receptors (ER+/PR- or ER-/PR+) with several well known prognostic factors and their possible influence on the incidence of local and distant failure, relapse free survival (RFS) and overall survival (OS) in women with early breast cancer treated at GOCS institutions. Methods: We evaluated 327 patients with stage I breast cancer (T1a,b,cN0M0; AJCC 2010) diagnosed between January 1991 and December 2009. Further analyses were conducted upon a cohort of 282 patients who were divided between those whose tumors expressed both HR and those with only 1HR. Results: The median age was 54.2 years (29-89). Median follow-up was 9.4±4.4 years (0.2-22.9). Both HR and 1HR were expressed in 242 and 40 patients respectively. Similar adjuvant treatment was administered in both groups although the number of mastectomies was higher in the subgroup with only 1HR (22.5% vs. 5.8%, P =. 0003). Univariate analyses showed no difference between both groups when correlated with age, body mass index, histologic type, T stage, histologic and nuclear grade, mitotic index, vascular invasion, necrosis and margin status. However, 1HR tumors had a higher rate of lymphovascular invasion (21.9% vs. 9.5%, P =.038) and HER2 expression (57.1% vs. 21.9%, P = .035). Treatment failure was more frequent in patients with only 1HR (12.5% vs. 5%, P =.064). Distant progression was also more common in this subgroup (80% vs. 58.3%, P =.334). There were no statistically significant differences in RFS and OS among groups. Conclusions: The expression of only 1HR constitutes a phenotype that could have a more aggressive biology and be associated with higher risk of recurrence than tumors with both receptors. Analysis of more patients, larger tumor size and N1 disease is warranted to confirm this hypothesis and have a better prognostic assessment.