Primary choriocarcinoma of the bladder evolving from a transitional cell carcinoma

A 67 year old man presented with haematuria, which on investigation was shown to be derived from a bladder tumour. The tumour initially was a typical transitional cell carcinoma except for rare trophoblastic cells. Over the next year and a half it gradually evolved into a choriocarcinoma. Postmortem examination confirmed that this was a primary choriocarcinoma of the bladder with no other sites of derivation shown.