PMC9462837_01
18F-FDG PET/CT revealed iso-metabolic metastases in the right peritoneum (A, yellow arrow), hypo-metabolic and low-density tumor necrosis after RFA in the right liver (A, red arrow) and low uptake in peritoneal metastases (A, white arrow). 18F-FAPI PET/CT showed increased diffuse uptake of metastases in the hepatic envelope (B, white arrow) and hepatic capsule (B, yellow arrows). 18F-FAPI PET/CT also showed a wedge-shaped high 18F-FAPI uptake disorder around the tumor necrosis lesion after RFA in the right liver (B, blue arrow). Increased diffuse 18F-FAPI uptake in the pancreas (B; white hollow arrows) indicated pancreatitis.
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Follow-up laboratory examinations showed that the serum alpha-fetoprotein (AFP) level increased progressively to 71.5 ug/L (reference range: 0-3 ug/L). 18F-FDG PET/CT and 18F-FAPI PET/CT were performed to further evaluate the nature of the lesion (Figure 1). 18F-FDG PET/CT revealed multiple iso-metabolic metastases in the right mesh membrane, hypo-metabolic tumor necrosis after RFA in the right liver, and low uptake in peritoneal metastases (Figure 1A). Astonishingly, 18F-FAPI PET/CT showed increased diffuse uptake of metastases in the hepatic capsule, which were negative in 18F-FDG PET/CT (Figure 1B). Furthermore, we accidentally observed wedge-shaped high 18F-FAPI uptake disorders around the tumor necrosis lesion after RFA in the right liver (Figure 1B, blue allow), consistent with the shape shown on MRI enhanced phase (Figure 2).
Enhanced liver MRI showed low signal intensity of hepatic capsular nodules on the arterial enhanced phase (A and B; yellow arrows) with high signal intensity on T2-phase (C, yellow arrow) and mild enhancement of the edge on the venous enhanced phase (D and E, yellow arrows). These lesions were resected, and metastases were confirmed by pathology (Figure 3). MRI on axial slices also showed a wedge-shaped high signal intensity around the tumor necrosis lesion after RFA in the right liver in the arterial and venous enhanced phases (B and D, blue allows).
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Furthermore, we accidentally observed wedge-shaped high 18F-FAPI uptake disorders around the tumor necrosis lesion after RFA in the right liver (Figure 1B, blue allow), consistent with the shape shown on MRI enhanced phase (Figure 2).
Elastic fiber staining (A, black arrow, magnification, x50), PAS staining (B, black arrow, magnification, x50) and Masson staining (C, black arrow, magnification, x50) showed a large of fibrous tissue with strong FAP expression in stromal cells in FAP staining (D, red arrow, magnification, x50) around the tumor necrosis lesion. Hematoxylin-eosin staining (E, magnification, x50) showed peritoneal metastatic hepatocellular carcinoma with strong FAP expression in stromal cells in FAP staining (F, red arrows, magnification, x100).
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RFA lesions with peripheral liver tissue were also resected, and histopathology confirmed complete necrosis of the tumor and surrounding benign hepatocyte degeneration and stromal fibrosis after RFA (Figure 3).