case_images: PMC10597670_01
case_images: Abdominal computed tomography showed an irregular mass on the anterior wall of the bladder, which involved all layers of the bladder.
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case_images: Computed tomography showed an ill-defined solid mass in the anterior wall of the bladder ( Figure 1 ).
case_images: Microscopic features of the surgical resection sample. (A) The urothelium and lamina propria of the bladder show no abnormalities (H&E, x100). (B) Bladder muscles were infiltrated to varying degrees by spindle cells. (H&E, x100). (C) Pump spindle cells were mixed with a predominantly plasmacytic infiltrate (H&E, x200). (D) The elongated spindle cells are arranged in a fascicular pattern (H&E, x200). (E) Hyperchromatic tumor cells are observed within the background of spindle cells (H&E, x400). (F) A few lipoma-like WDL components are identified (blue arrow, H&E, x100).
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case_images: Microscopically, the urothelium and lamina propria of the bladder showed no abnormalities ( Figure 2A ). The muscle layer of the bladder and peripheral adipose tissue contained spindle cells, which were arranged in a fascicular growth pattern with mild to moderate atypia and hyperchromatic nuclei, mimicking low-grade fibroblastic tumors ( Figure 2B ). Pump spindle and scattered inflammatory cells were observed in the superficial layer of the muscularis propria ( Figure 2C ). Additionally, in the deep layers of the muscularis propria and serosa, slender spindle cells arranged in a fascicular growth pattern were separated by abundant eosinophilic collagen ( Figure 2D ). Bizarre and hyperchromatic stromal cells were observed in these areas ( Figure 2E ). Notably, small foci of typical lipoma-like WDL components were identified within the background of the spindle cell tumor using extensive sampling ( Figure 2F ).
case_images: The tumor components of the sample were positive for MDM2 (A) and CDK4 (B) and focal positivity for P16 (C) (immunostaining, x400). (D) FISH showed amplification of MDM2 and CDK4 in most neoplastic cells (left part: MDM2; right part: CDK4; red signals represent MDM2 and CDK4, respectively. Green signals represent chromosome 12 centromeres (magnification: x1000).
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case_images: Immunohistochemically, the neoplastic cells were positive for MDM2 ( Figure 3A ), CDK4 ( Figure 3B ), P16 ( Figure 3C ), smooth muscle actin (SMA), and focal positivity for muscle-specific antigen (MSA). FISH revealed MDM2 and CDK4 amplification in the spindle cells and adipocytes of the tumor ( Figure 3D ), whereas negative results was observed in the adipose components surrounding the bladder wall.