Routine immunohistochemical markers, i.e., pan-cytokeratin, epithelial membrane antigen, villin, caudal-type homeobox 2, E-cadherin, and p53, were positive in the gastric pleomorphic giant cell carcinoma, while vimentin, calponin, smooth muscle actin, nestin, S-100, cluster of differentiation (CD) 99, desmin, and CD34 were focally expressed in both the spindle and the giant cells, with Ki-67-positive cells accounting for 70–80%. The gene discussed is ADA2; the disease is lung giant cell carcinoma.