Non-muscle-invasive bladder cancer (NMIBC) is the most common type of bladder cancer presentation and is characterized by a varying probability of recurrence and progression. Sporadically, patients with NMIBC might also develop tumour metastases without any pathological evidence of muscle-invasive disease within the bladder, a condition known as metastatic NMIBC. In the published literature, this phenomenon is limited to several case reports and small reviews, with few data regarding the possible aetiologies. Several possible factors can be potentially associated with metastatic NMIBC, including tumour understaging, the number of transurethral resection procedures received by the patient, the presence of circulating tumour cells, the modality used for diagnostic cystoscopy and possible gender-associated differences. In this Perspective, our aim was to integrate and report currently available data on this relatively rare entity and provide some potential aetiological explanations.

非肌层浸润性膀胱癌 （NMIBC） 是最常见的膀胱癌表现类型，其特征是复发和进展的可能性不同。偶尔，NMIBC 患者也可能在膀胱内没有任何肌层浸润性疾病的病理证据的情况下发展为肿瘤转移，这种情况称为转移性 NMIBC。在已发表的文献中，这种现象仅限于几篇病例报告和小型综述，关于可能病因的数据很少。几个可能的因素可能与转移性 NMIBC 相关，包括肿瘤分期不足、患者接受的经尿道切除术次数、循环肿瘤细胞的存在、用于诊断膀胱镜检查的方式以及可能的性别相关差异。在这个观点中，我们的目标是整合和报告有关这种相对罕见的实体的当前可用数据，并提供一些可能的病因学解释。