Follicular dendritic cell sarcoma is a very rare bladder tumor with very few cases that have been reported in the English literature. We report an unusual case of follicular dendritic cell sarcoma that is coexistent with urothelial carcinoma (UC) in the urinary bladder of a 73-year-old man, who first presented with lower abdominal pain. Microscopic examination of the first transurethral resection of bladder tumor (TURBT) sample showed a neoplasm containing spindle or ovoid-shaped cells that were arranged in storiform, nested or swirling patterns. Abundant mitotic Figs. (30 mitoses/10 high-power fields) and apoptotic bodies were present. The tumor cells were positive for CD21 and vimentin, partly positive for CD23, D2–40 and CD35. After 6 weeks, the tumor recurred lately, which surprisingly contained a component of urothelial carcinoma. The first TURBT sample was then reviewed and a coexisting UC mixed with FDCS was identified by examining the deeper levels of the tumor blocks. This case is, to our knowledge, the first time to report the coexistence of FDCS and UC in the urinary bladder of an elderly patient. And these two tumors may share a similar molecular mechanism.

中文翻译：

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并发尿路上皮癌的膀胱滤泡性树突状细胞肉瘤（FDCS）–病例报告

滤泡性树突状细胞肉瘤是一种非常罕见的膀胱肿瘤，英国文献中报道的病例很少。我们报告了一个不寻常的滤泡性树突状细胞肉瘤病例，该病例与一个73岁男性的膀胱尿路上皮癌（UC）共存，该男性首次出现下腹痛。膀胱肿瘤（TURBT）的首次经尿道切除术的显微镜检查显示，肿瘤中含有梭形或卵形细胞，呈梭形，巢状或涡旋状排列。丰富的有丝分裂无花果。（30 mitoses / 10 high-power field）和凋亡小体存在。肿瘤细胞对CD21和波形蛋白呈阳性，对CD23，D2-40和CD35部分呈阳性。6周后，该肿瘤近来复发，其令人惊讶地包含尿路上皮癌的成分。然后检查第一个TURBT样品，并通过检查更深的肿瘤块水平来确定与FDCS混合存在的UC。据我们所知，该病例是首次报道老年患者膀胱中FDCS和UC的共存。而且这两种肿瘤可能具有相似的分子机制。