Further immunohistochemical analysis of 103 breast tumors of the UNC337 data set revealed that compared to the basal-like subtype, the claudin-low tumor subtype had a preponderance for low to absent expression of E-cadherin and claudin 3 (45% vs. 11% for E-cadherin, P < 0.05; 59% vs. 11% for claudin 3, P < 0.005; χ2 test). The gene discussed is CLDN3; the disease is breast neoplasm.