Increasing levels of several proteins were associated with a statistically significant higher likelihood for incomplete tumor resection (defined by the presence of postoperative residual tumor) in the training cohort, including ERK (OR 4.4, p = 0.002), extracellular HER2 (OR 3.3, p = 0.02), HER2 (OR 2.2, p = 0.05), and HER3 (OR 1.5, p = 0.04). The gene discussed is ERBB2; the disease is neoplasm.