SPP1 and neoplasm: Neither mean percentage OPN staining by IHC nor mean baseline OPN plasma level differed significantly by T stage (T0-1 vs T2 to 4), tumor grade (1 vs 2 vs 3), nodal status (negative vs positive), hormone receptor status (negative vs positive), age (<60 years vs older), race (Caucasian vs other), or body mass index (in quartiles).