Micropapillary bladder carcinoma: a clinicopathological study of 20 cases

Micropapillary bladder carcinoma is rare, with only 18 cases reported to date. We report 20 additional cases with long-term followup.

A total of 680 patients with an initial diagnosis of bladder carcinoma in western Sweden in 1987 and 1989 were prospectively registered. The clinical records of all 816 patients with bladder cancer treated at Sahlgrenska University Hospital with external beam irradiation between 1962 and 1989 were reviewed. The histopathological material was reviewed and immuno-histochemical analyses were performed on 20 cases identified with micropapillary bladder carcinoma.

The incidence of micropapillary bladder carcinoma was 0.7%. Mean patient age at diagnosis was 69 years (range 45 to 82) and the male-to-female ratio was 2.3:1. All but 5 patients had stage T3a disease or higher. There was no difference in stage or prognosis between the 5 prospectively identified patients and those treated with external beam irradiation. Only 2 patients had micropapillary bladder carcinoma as the only pattern, while 1 had 10% and the remainder had 20 to 95% micropapillary bladder carcinoma. Transitional cell carcinoma was noted in 17 patients and 5 had areas of gland forming adenocarcinoma. Carcinoma in situ was noted in 13 patients and 15 had lymphatic invasion. Only 5 patients survived 5 years, 1 of whom died of bladder cancer after 7 years. Radiation and chemotherapy did not seem to be effective.

The light microscopic appearance, which is strikingly similar to ovarian papillary serous carcinoma, and immunohistochemical staining pattern lend some support to the theory that micropapillary bladder carcinoma is a variant of adenocarcinoma. Since even the focal presence of micropapillary bladder carcinoma is associated with a poor prognosis, recognition of this entity is important. Due to its rarity, the optimal treatment of micropapillary bladder carcinoma needs to be determined in a multicenter study.