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.

Lymphoepithelioma-like carcinoma is diagnosed in less advanced stages and has a more favorable long-term prognosis than other types of undifferentiated invasive carcinomas of the bladder. Our data and review of the literature suggest that lymphoepithelioma-like carcinoma should be treated stage by stage like other bladder carcinomas.

Primary small cell carcinoma of the bladder is a rare condition with approximately 100 cases reported to date. An incidence of 0.7% small cell carcinoma was found in a total series of bladder tumors diagnosed in Western Sweden during a 2-year period. We describe 22 patients with primary small cell carcinoma followed to death or for at least 6 years. Three additional cases were diagnosed at autopsy. Of 18 patients with stages T2M0 to T4M0 cancer treated with locoregional therapy 5 (28%) had no evidence of disease after a median observation of 10 years (range 6 to 18) and 13 died of disease after 0.5 to 19 months (median 7.3). Two patients with metastatic disease were treated with systemic chemotherapy but died within 15 months. Two patients died shortly after the diagnostic biopsy. Our study and a review of the literature indicate that primary small cell carcinoma of the bladder is less aggressive than its pulmonary counterpart and that some patients can be cured by transurethral resection, or partial or radical cystectomy combined with radiotherapy.