In urothelial carcinoma high CLDN3 staining was associated with high grade in non-invasive carcinomas (p < 0.0001), tumor invasiveness (pTa vs. pT2-4; p < 0.0001) as well as with nodal metastasis (p = 0.0111) and lymphovascular invasion (L1 status; p = 0.0062) in the subset of muscle-invasive carcinomas. This evidence concerns the gene CLDN3 and invasive carcinoma.