EGFR and neoplasm: The tumor tissue showed 110-kDa sEGFR isoforms with isoelectric point (pI) >6, while plasma samples showed 110-kDa sEGFR isoforms with an extremely acidic pH (3.87–4.74), indicating that the secreted EGFR isoforms in plasma and in lung cancer were molecularly heterogeneous [50].