TGFB1 and urinary bladder small cell neuroendocrine carcinoma: It could be speculated that already the compact growth pattern of small-cell cancers hampers immune cell infiltration, but small-cell bladder carcinomas may also develop established molecular immune escape mechanisms including physical or chemical barriers, such as extracellular matrix remodeling or TGF-beta-1 upregulation [11, 22–24].