case_images: PMC10102936_01
case_images: Representative axial positron emission tomography/computed tomography
  (PET/CT) images demonstrating the gallbladder mass (arrows, CT image on left
  with corresponding PET image on right).
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case_images: This PET/CT scan demonstrated a decrease in the size of her lung mass and a 2 cm hypermetabolic polypoid mass in the GB (Figure 1) highly concerning for a primary GB carcinoma that was first seen on prior PET/CT.
case_images: Gross photograph of polypoid fundic gallbladder mass.
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case_images: The GB grossly demonstrated a polypoid fundic mass on the hepatic side of the GB wall, with focal discoloration of the overlying mucosa (Figure 2).
case_images: Hematoxylin & eosin (H&E) and immunohistochemical (IHC) stains of the
  gallbladder mass. (a) Low-power H&E image showing adjacent normal
  gallbladder mucosa and the hypercellular tumor with geographic necrosis
  visible (20x). (b) High-power H&E image demonstrating vaguely organoid
  cellular architecture, the cells show variable cytoplasm with frequent
  mitoses and apoptosis (200x). (c) IHC stain for synaptophysin is diffusely
  positive (20x). (d) IHC stain for Ki67 demonstrates a proliferative index of
  approximately 80% (20x).
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case_images: Histologically, sections demonstrated a hypercellular tumor with areas of geographic necrosis the adjacent GB mucosa was unremarkable (Figure 3(a)). Cytologically, the cells demonstrated variable amounts of cytoplasm, with vesicular-granular chromatin, prominent nucleoli, frequent mitotic figures, apoptotic bodies, and pleomorphism (Figure 3(b)). TTF1; with a Ki67 proliferative index of approximately 80% (Figure 3(d)). The findings were most consistent with an LCNEC involving the GB.