Vitamin D deficiency is associated with poor breast cancer prognostic features in postmenopausal women

•Vitamin D (VD) deficiency could play an important role in the prognostic features of breast cancer.•Serum level of 25 hydroxyvitamin D was measured in all patients up to 20days post-diagnosis.•Sufficient VD levels were detected in 33.8% of patients, while deficient levels in 66.2% of cases.•VD deficiency was associated with positive axillary lymph node status, negative estrogen receptor and high Ki-67.•All cases of triple negative were detected in VD deficient women. This study aimed to evaluate the association between pretreatment vitamin D (VD) deficiency with breast cancer prognostic features in Brazilian postmenopausal women. An analytical cross sectional study was conducted with 192 women, aged 45–75 years, attended at University Hospital. Women with recent diagnosis of breast cancer, in amenorrhea >12months and age ≥45 years, without medication use or clinical conditions that interfere with VD values were included. Clinical and anthropometric data were collected. Serum level of 25 hydroxyvitamin D [25(OH)D] was measured in all patients until 20days after breast cancer diagnosis, and was classified as normal (≥30ng/mL), insufficiency (20–29ng/mL) and deficiency (