To examine the relevance of PRL-3 with ERK1/2 activity in colon cancer, expression of PRL-3 and p-ERK1/2 in 11 pairs of consecutive 4-μm primary lesions from sporadic colon cancer patients was evaluated by an immunohistochemical assay with anti-PRL-3 and anti-p-ERK1/2 antibodies, respectively. The gene discussed is PTP4A3; the disease is colonic neoplasm.