PMC4602642_01
Abdominal computed tomography images (case 1): coronal (A), sagittal (B), and axial (C and D) reconstructions. Computed tomography of the abdomen showed an ill-defined multilocular low-density mass measuring 13 x 8 x 7 cm in the pelvis and lower abdomen.
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F1
An intravenous contrast-enhanced computed tomography (CT) scan showed an ill-defined multilocular soft tissue tumor measuring 13 cm x 8 cm x 7 cm in the pelvis and lower abdomen (Figure 1).
PMC4602642_02
Endoscopy appearance of GI PEComa (case 2). White light (A) and narrow band imaging (B) endoscopy showed a 2-cm diameter, polypoid tumor protruding into the lumen of the terminal ileum. GI PEComa = perivascular epithelioid cell tumors of gastrointestinal tract.
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F2
An enteroscopy displayed a 2-cm diameter, polypoid, submucosal tumor in the terminal ileum (Figure 2).
Resected specimens of perivascular epithelioid cell tumor arising in the terminal ileum (case 1).
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F3
On gross examination, an ill-defined tumor measuring 13.5 x 7.5 x 7.0 cm was found at the terminal ileum about 12 cm from ileocecal valve (Figure 3).
Microscopic features of the ileum tumor (case 1). The tumor consisted of an epithelioid cell proliferation with a vaguely nested pattern (A). In some areas, the tumor displayed a pseudoglandular histological appearance (B). The perivascular epithelioid cells had clear to eosinophilic granular cytoplasm with some slightly irregular nucleus nuclei (C). Foci of coagulation necrosis were also found in the tumor (D). The tumor cells were positive for HMB45 (E), pSTAT3 (F), and TFE3 (G), and negative for Cyclin D1 (H).
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F4
Microscopically, the tumor showed epithelioid cell proliferation with a vaguely nested pattern (Figure 4A). Some areas showed a pseudoglandular histological appearance (Figure 4B). Some slightly irregular nuclei with scattered prominent nucleoli were focally present (Figure 4C). Foci of tissue necrosis and occasional mitoses (3~5/50HPF) were found in the tumor (Figure 4D). Immunohistochemically, the tumor cells were positive for HMB45, TFE3, and pSTAT3 (Figure 4E-4G), whereas all other markers tested were negative (Table 1).
Cross-section of perivascular epithelioid cell tumor arising in the terminal ileum (case 2).
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F5
On cut section, the tumor was well-circumscribed but not encapsulated (Figure 5).
Microscopic features of the ileum tumor (case 2). The tumor showed clear spindle-shaped cells arranged in fascicular and nesting patterns (A and B). The tumor cells expressed HMB45 (C), SMA (D), and PR (F). SMA = smooth muscle actin, PR = pathogenesis-related protein
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F6
Histologic examination revealed clear spindle-shaped cells arranged in fascicular and nesting patterns, separated by thin fibrovascular septa (Figure 6A-B). Immunohistochemical analysis revealed that the tumor cells expressed HMB45, Melan-A, SMA, HHF35, Desmin, and pathogenesis-related protein (Figure 6C-F), and were negative for all other markers tested (Table 1).