Urothelial (transitional cell) carcinoma (UC) is the most common type of bladder cancer in humans, dogs and cats, although the incidence in cats is comparatively low. This retrospective study details the histopathological features of UC of the urinary bladder in 38 samples from 35 cats. Of the 38 samples, eight had a papillary architecture and in nine the tumour cells formed tubular or acinar structures. Tumour cell invasion of the bladder wall varied from confinement within the lamina propria or submucosa to transmural or extending to the serosa. The tumour stroma varied from sparse to abundant, with a scirrhous, myxomatous or mucinous appearance in eleven cases, three cases and one case, respectively. The degrees of tumour cell necrosis and inflammation were highly variable. We confirm that the histopathological features of bladder UC in cats have many similarities to the corresponding tumours in dogs and humans.

尿路上皮（移行细胞）癌 (UC) 是人类、狗和猫最常见的膀胱癌类型，尽管猫的发病率相对较低。这项回顾性研究详细介绍了来自 35 只猫的 38 个样本中膀胱 UC 的组织病理学特征。在 38 个样本中，8 个具有乳头状结构，9 个肿瘤细胞形成管状或腺泡状结构。膀胱壁的肿瘤细胞侵袭从固有层或粘膜下层内的限制到透壁或延伸至浆膜不等。瘤间质由稀疏到丰富，分别呈硬质、粘液样或粘液样11例、3例、1例。肿瘤细胞坏死和炎症的程度是高度可变的。