PMC8510831_01
(a) Coronal CT image of the abdomen and pelvis with oral contrast demonstrates an intraluminal mass in the terminal ileum and ascending colon (arrow) serving as a lead point for ileocolic intussusception. (b) Axial T1 fat-saturated postcontrast MRI of the abdomen demonstrates multiple peripherally enhancing lesions throughout the liver consistent with liver metastasis.
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Abdomen/pelvic computed tomography (CT) demonstrated ileocecal intussusception, with a 5 cm mass as the lead point (Figure 1(a)). A fluorescence in situ hybridization (FISH) study confirmed TFE3 (Xp11.23) gene rearrangement with no evidence of ASPSCR1 gene fusion. The diagnosis of localized PEComa with a high-risk malignant potential was conferred. A follow-up image at 3 months postoperation detected metastatic recurrence diffusely involving but isolated to the liver (Figure 1(b)) that was confirmed by a core biopsy.
(a) The histologic features of the tumor which were composed of nests and sheets of epithelioid cells with frequent melanin pigmentation separated by thin-walled capillary vessels (predominant alveolar architecture) (hematoxylin and eosin (H&E) staining, magnification x200). Tumor cells demonstrate immunohistochemical reactivity for (b) TFE3, (c) HMB45, and (d) Melan A (b-d, magnification x200).
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Microscopically, the tumor was composed of nests and sheets of uniform epithelioid cells with a pale eosinophilic cytoplasm separated by thin-walled capillary vessels (Figure 2(a)). TFE3 (Figures 2(b)-2(d)), and inhibin and negative for cytokeratin, PAX8, CD117, DOG1, smooth muscle actin, desmin, S100, and neuroendocrine markers.