Transitional cell carcinoma of the urinary bladder with osteoclast-type giant cells: a report of two cases and review of the literature.

We report two transitional cell carcinomas of the urinary bladder containing numerous osteoclast-type giant cells that stained for vimentin and acid phosphatase (with and without tartrate) and were negative for cytokeratin and lysozyme. One tumour, in a 65-year-old man, was composed of papillary transitional cell carcinoma, invasive poorly differentiated carcinoma with a prominent spindle cell component and numerous osteoclast-type giant cells; repeat curettage 2 months later showed no residual tumour. The second tumour occurred in a 75-year-old woman who underwent a radical cystectomy for a deeply invasive transitional cell carcinoma with a spindle and anaplastic giant cell component and areas containing numerous osteoclast-type giant cells. Osteoclast-type giant cells, which appear to be reactive, should be distinguished from the neoplastic giant cells of giant cell carcinoma.