NR4A1 and neoplasm: The protective effect of vitamin D against breast tumor progression was introduced first time by Garland in 198022 and during the following years many studies have demonstrated this association.15,16,23,24 In recent years, researchers have focused on the relationship between vitamin D levels and breast cancer prognostic factors such as tumor size, histologic grade and stage of the disease, lymph node involvement, hormone receptor status and metastasis.