We report an extremely rare case of a primary angiomyolipoma arising in the spleen. A 80-year-old woman diagnosed with gastric adenocarcinoma was found in abdominal computed tomography (CT) to have an irregular 14-cm mass in the left upper quadrant with potential infiltration into the pancreas. She had no kidney or liver abnormalities and no clinical evidence of tuberous sclerosis. Abdominal angiography showed that the mass corresponded to a hypervascular tumor in the spleen, radiologically interpreted as malignant tumor and necessitating splenectomy. The resected 14 × 12 × 9-cm spleen containing the tumor weighed 444g and contained yellow nodules and irregular cysts in the splenic parenchyma without necrosis or bleeding foci. Histopathologically, the tumor consisted of mature adipose tissue, dilated blood vessels associated with wall thickening, and atypical smooth muscle cells associated with marked morphological pleomorphism. Immunohistochemically, tumor cells were positive for HMB-45, α-SMA, and desmin and negative for CD68. The Ki67/MIB1 labeling index was 1-3%, yielding a definitive diagnosis of angiomyolipoma arising in the spleen based on histological and immunohistochemical findings. Only one case of angiomyolipoma arising in the spleen has been reported in the global literature.
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