ObjectiveThe aim of this study was to determine the correlation between the primary tumor (PT) maximum standardized uptake value (SUVmax) and breast cancer prognostic factors, overall survival, and relapse-free survival on the basis of histopathological and molecular characteristics.Patients and methodsIn this retrospective study, 436 female patients with breast cancer were evaluated following a pretreatment F-18-FDG PET/CT scan. The PT SUVmax and histopathological/molecular characteristics were determined from primary tumor tissues and analyzed using the Mann-Whitney U and Kruskal-Wallis tests.ResultsThe median SUVmax of 436 PT was 10.1 (1.7-72). The PT SUVmax values were higher in ER- versus ER+ (P=0.001), PR- versus PR+ (P=0.001), Her2+ versus Her2- (P=0.01), Ki-67% of at least 20 versus Ki-67% of less than 20 (P<0.001), histological grade 3 versus grade 1-2 (P<0.001), nuclear pleomorphism score 3 versus score 1-2 (P<0.001), and mitotic score 3 versus score 1-2 patients (P<0.001). The lowest SUVmax levels were observed in the LumA group and the highest SUVmax levels were observed in the Her2 group (P<0.001). LumA patients with PR values greater than 20% had lower PT SUVmax values than the patients with PR values of 20% or less (P=0.023). The PT SUVmax was higher in patients with recurrence (P=0.03) and died related to disease (P<0.001) independent of time.ConclusionThe PT SUVmax showed a significant correlation with most of the prognostic factors and histopathological subtypes as a noninvasive tool. It is also usable in the prediction of tumor-related deaths or relapse independent of time. Our results could guide future studies to provide new histopathologic subtype definitions on the basis of new PR criteria.