Signet ring cell carcinoma of bladder: a dilemma between primary and metastatic.

Signet ring cell carcinoma, in general, is a peculiar tumour. There is always a query regarding its exact site of origin. Even, immunohistochemistry shows overlapping staining patterns between various sites. On one hand, signet ring cell carcinoma of the bladder is a rare occurrence, but on the other hand metastatic signet ring cell carcinoma to the bladder is not uncommon. However, without prior knowledge of the primary site of tumour clinically and radiologically, definitive diagnosis is challenging based on morphology and immunohistochemistry. [ABSTRACT FROM AUTHOR]