Molecular and morphological differences between tumor periphery and center. Formalin fixed liver sections with CRC liver metastases were stained for hypoxia by staining for pimonidazole using hypoxiprobe and growth factor/receptor expression HIF1a, VEGF, AT1R , b-FGF and TGF-β using the respective antibodies. (A) Low magnification scale bar=500μm, inset magnification scale bar=50μm, Tumors in the periphery show less hypoxia (first row panel 1 and inset 2) unless the tumor periphery lies on the liver surface with no adjacent host tissue (inset 1). (B) HIF1a staining displaying higher staining towards the tumor center in areas associated with high hypoxia. (C) VEGF, (D) AT1R, (E) b-FGF and (F) TGF-β, all are expressed at higher levels in the tumor periphery. (B-F magnification scale bar=200μm). (G) Quantification of AT1R, VEGF, TGF-β, demonstrate significantly higher staining in the periphery (p<0. 0001, p<0. 001, and p<0.0001 respectively).