Primary small cell carcinoma of the urinary bladder.

Small cell carcinoma of the urinary bladder (SCCB) is an extremely rare but aggressive tumour constituting less than 0.7% of all urinary bladder tumours. It is often misdiagnosed as transitional cell carcinoma, owing to the similarities in presentation. Diagnosis of SCCB is based on the WHO criteria for small cell lung carcinoma. A 58-year-old man who had presented with haematuria and burning micturition for 3 months was initially diagnosed as high-grade muscle-invasive urothelial carcinoma based on the TURBT specimen. The patient was put on neoadjuvant chemotherapy, but presented again with haematuria and back pain after 3 months. Imaging studies showed a lesion in the posterolateral wall of the urinary bladder, along with partial collapse and anterior wedging of L1 vertebra. He underwent TURBT, and on the basis of histopathology and immunohistochemistry, a diagnosis of primary SCCB bladder with vertebral metastasis was made.