case_images: PMC10867255_01
case_images: MRI plain scan, DWI, and enhanced image of the hepatic PEComa are presented. The hepatic PEComa exhibited a slightly prolonged T1 signal (A) and a slightly prolonged T2 signal (B). The DWI showed restricted diffusion (C). The enhancement pattern was characterized by fast-in and fast-out. During the arterial phase, a significant enhancement was observed, with a considerably higher degree of enhancement compared to the adjacent normal liver parenchyma (D). Subsequently, in the portal vein phase (E) and delayed phase (F), the enhancement gradually subsided and ultimately became less pronounced than the surrounding liver parenchyma (white arrows indicate the tumor).
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case_images: Moreover, arterial enhancement was observed with rapid clearance during the delayed phase ( Figure 1 ).
case_images: Showcase hepatic PEComa images obtained from 18F-FDG and 68Ga-FAPI PET/CT scans. (A) The maximum intensity projection (MIP) image generated from the FDG scan revealed a lack of tumor uptake in the liver. (B, C) Axial images acquired from CT and fused FDG PET/CT scans exhibited a mildly hypodense lesion in liver segment V, accompanied by minimal tumor radioactivity uptake, characterized by SUVmax = 1.31 and TBRmax = 0.83. (D, E) Axial images derived from CT and fused FAPI PET/CT scans demonstrated robust tumor radioactivity uptake at the same location, with SUVmax = 5.28 and TBRmax = 10.56. (F) The MIP image generated from the FAPI scan displayed avid tumor uptake in the liver (white arrows indicate the tumor).
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case_images: There was no focal activity typical of hypermetabolic malignancy on the MIP image ( Figure 2A ). The lesion was non-FDG avid with an SUVmax of 1.31 (in comparison to the normal hepatic SUVmax of 1.58), and the maximum tumor-to-background ratio (TBRmax) was 0.83 ( Figures 2B, C ). Interestingly, 68Ga-FAPI PET/CT MIP, transaxial CT, and transaxial fused images ( Figures 2D-F ) demonstrated intense FAPI uptake (SUVmax, 5.28; TBRmax, 10.56) in the hepatic lesion.
case_images: Histological and immunostaining analysis of hepatic PEComa. (A) Histological examination using hematoxylin and eosin (HE) staining revealed hepatic PEComa. Immunohistochemical markers HMB45 (B) and Melan-A (C) for melanocytic, SMA (D) for smooth muscle, and FAP (E) exhibited positive expression. Conversely, immunohistochemical markers glypican-3 (F), hepatocyte (G), arginase-1 (H), and AFP (I) for HCC, CK19 (J) and CK7 (K) for intrahepatic cholangiocarcinoma, desmin (L) for muscle tissue, SOX-10 (M) and S-100 (N) for nerve and melanoma, and PCK (O) for broad-spectrum epithelial tumors demonstrated negative expression. (P) the Ki-67 LI was merely 3%, indicating a low proliferation rate and benign biological characteristics.
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case_images: Subsequently, the patient underwent laparoscopic partial hepatectomy of segment V, and hematoxylin and eosin (HE) staining indicated predominantly epithelioid tumor cells without significant atypical features, tumor necrosis, or pathological mitosis ( Figure 3A ). Immunohistochemistry analyses yielded positive results for HMB45, Melan-A, SMA, and FAP ( Figures 3B-E ), but negative for glypican-3, hepatocyte, arginase-1, AFP, CK19, CK7, desmin, SOX-10, S-100, and PCK ( Figures 3F-O ). The hepatic PEComa also presented a low Ki-67 labeling index (LI) of 3% ( Figure 3P ).