case_images: PMC10864482_01
case_images: (A) Cross-sectional image of the contrast-enhanced abdominal computed tomography (CT) scan demonstrated a 1.6-cm nodule (yellow solid line) adjacent to the gallbladder with significant enhancement during the arterial phase. (B) The nodule showed continuous enhancement in the portal phase.
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case_images: The patient further completed an enhanced abdominopelvic computed tomography (CT) scan, which reported a round-like soft tissue density shadow with a diameter of approximately 1.6 cm in the hepatic hilar region, and the enhanced scan showed significant enhancement in the arterial phase and continuous enhancement to the portal phase ( Figure 1 ). Supplementary Figure 1A ). Single-photon emission computed tomography (SPECT)/CT fusion imaging further clarified the localization of the tumor ( Supplementary Figure 1B ).
case_images: (A) Gross photograph of the tumor (yellow arrow) and gallbladder. (B) The tumor together with a portion of the gallbladder has been sectioned, revealing a close relationship between the tumor and the gallbladder. The tumor is located in the neck of the gallbladder and near the opening of the cystic duct.
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case_images: In the macroscopic view of the tumor shown in  Figures 2A, B , a smooth tumor was located in the neck of the gallbladder. The examination of immunohistochemistry performed on paraffin-embedded sections confirmed a primary neuroendocrine tumor originating from the gallbladder, with 2% of cells staining positive for Ki-67 ( Figure 3D ) and mitotic figures <2 for 10 HPF.
case_images: (A, B) The tumor is located in the muscular layer of the gallbladder. (C) Immunohistochemical staining for gastrin shows strong and diffuse positive in tumor cells (magnification, x200). (D) NET with a low Ki-67 proliferation index (magnification, x100). NET, neuroendocrine tumor.
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case_images: The examination of immunohistochemistry performed on paraffin-embedded sections confirmed a primary neuroendocrine tumor originating from the gallbladder, with 2% of cells staining positive for Ki-67 ( Figure 3D ) and mitotic figures <2 for 10 HPF. Microscopic examination confirmed the source of the tumor, which was located in the muscular layer of the gallbladder ( Figures 3A, B ). Immunohistochemical staining for gastrin showed strong positive and diffuse positive staining in tumor cells ( Figure 3C ).