Myxoid cystitis with "chordoid" lymphocytes: another mimic of invasive urothelial carcinoma.

Invasive urothelial carcinoma is characterized by a number of histologic variants that can sometimes lead to diagnostic difficulty. In addition to those described by the World Health Organization, 2 additional variants have recently been described, invasive urothelial carcinoma with chordoid features and urothelial carcinoma with abundant myxoid stroma, both being characterized by the presence of a prominent myxoid stroma. This report describes a peculiar type of cystitis that closely mimicked myxoid urothelial carcinoma. A transurethral resection specimen from a 73-year-old woman with an earlier diagnosis of invasive urothelial carcinoma focally displayed rounded, epithelioid cells arranged in a corded manner and separated by myxoid stroma; this was originally misinterpreted as recurrent invasive carcinoma. A review of the case with immunohistochemical studies showed the component cells to be polyclonal B-lymphocytes, based upon which the diagnosis of malignancy was reversed. This peculiar form of cystitis, herein termed myxoid cystitis with "chordoid" lymphocytes, has not been described earlier and should be considered among the mimics of invasive urothelial carcinoma, especially those with a myxoid stroma.