PBRM1 and urothelial carcinoma: Next, n = 116 samples of patients with pure squamous cell carcinoma (n = 68) and mixed urothelial carcinoma with substantial squamous differentiation (n = 48) were analyzed for seven SWI/SNF complex proteins (ARID1A, SMARCA4, SMARCB1, SMARCC1, SMARCC2, SMARCA2 and PBRM1) by immunohistochemistry (Figure 2A).