71 © The Editor(s) (if applicable) and The Author(s), under exclusive license to Springer Nature Switzerland AG 2021 S. S. Goonewardene et al., Management of Muscle Invasive Bladder Cancer, Management of Urology, https://doi.org/10.1007/978-3-030-57915-9_11 11 MIBC and Micropapillary Bladder Cancer 11.1 Histopathology of Micropapillary Bladder Carcinoma The micropapillary variant of urothelial carcinoma (MPUC) is a rare but well- recognized tumour [1]. It is more aggressive compared to conventional urothelial carcinoma. They demonstrate variable keratin 7, keratin 20 and human epidermal growth factor receptor 2 (Her 2)neu expression [1]. The tumour presents with hae- maturia [1]. The micropapillary pattern was seen in 20–95% [1]. All showed exten- sive lymphatic emboli with detrusor muscle invasion [1]. Lymph node metastasis was present in all except one. They all underwent cystoprostatectomy [1]. Keratin 7 and abluminal pattern of EMA positivity were seen in 100%. Keratin 20 was posi- tive in fve cases (71%). Her 2neu positivity was seen in four cases [1]. Three patients died 2, 3, and 6 months after initial diagnosis—two were Her 2 positive, one was Her 2 negative [1]. There was no clear prognostic signifcance of Her 2 positivity. Micropapillary carcinoma (MPC) is so aggressive and needs early recognition and treatment [2]. González-Peramato et al. [2] determined whether this can be recognized with cytology. On histology, 14 cases were infltrative, while 6 were exclusively superfcial [2]. Cytology was characterized by numerous small, cohe- sive groups and single neoplastic cells [2]. Pseudopapillae were present in 17 cases and in 9 they were a relevant fnding. Morules were present in 15 cases. Isolated microacini were seen in 14 cases. Infltrative tumours showed more neoplastic groups [2]. Cellular atypia was prominent in 17 cases. In 15 cases, a cytologic diag- nosis of urothelial carcinoma was made. One case was diagnosed as adenocarci- noma. The remaining 4 cases were considered suspicious of malignancy [2]. Immunohistochemical staining demonstrated that both micropapillary and asso- ciated conventional urothelial carcinomas were positive for MUC1 and 2, cytokera- tin 7, PTEN, p53, and Ki-67. Her2Neu, uroplakin, cytokeratin 20, 34betaE12, CA125, and p16 were positive in 4, 10, 8, 7, 3, and 3 cases, respectively [3].