Study demographics and clinical variables. (A) For the period 30 August 2010 to 31 August 2013, yearly (non-calendar) summary of the number of enrolled patients, the number of patients with preoperative blood sample collected, and number of patients with tumor specimen collected. (B-H) For the two complete calendar years 2011 and 2012 that could be matched to the INCA Swedish national breast cancer registry, (B) chart of all cases with a preoperative diagnosis of primary breast cancer within the catchment region divided into those that were accrued or not accrued. Comparison of baseline clinical variables between all eligible breast cancer patients, patients accrued, and patients accrued with tumor sample, for (C) estrogen receptor (ER) status, (D) progesterone receptor (PgR) status, (E) HER2 status, (F) age at diagnosis, (G) Nottingham histological grade (NHG), and (H) tumor size. †,‡ Significant differences were identified between all diagnoses and accrued with tumor specimen for NHG (P = 0.005) and tumor size (P <0.001), and between patients accrued and accrued with biopsy for NHG (P = 0.025) and tumor size (P <0.001).