Radiologic findings in early-stage cancers are often subtle and can overlap with those of chronic inflammatory conditions. Established risk factors include cholelithiasis along certain geographic locations (Gangetic belt) , porcelain gall bladder, adenomyomatosis, gall bladder polyps and xanthogranulomatous cholecystitis. The TNM staging is based on 8th American Joint Committee on Cancer (AJCC) staging system. T category has now been subdivided into T2a and T2b based on the tumor’s location. Nodal categories are defined as N1 (1-3 metastatic lymph nodes) and N2 (≥ 4 metastatic lymph nodes) in the 8th edition and recommends to examine more than six lymph nodes for accurate staging of the nodal category.

Precursor lesions: 

Precursor lesions of gallbladder carcinoma (GBC) are conditions that increase the risk of malignant transformation. Radiological imaging plays a crucial role in detecting and monitoring these lesions. The main precursor lesions include:

1. Gallbladder Polyps

• Radiologic Features (Ultrasound, CT, MRI)
  • Non-mobile, non-shadowing echogenic lesions attached to the gallbladder wall.
  • Polyps >10 mm or showing rapid growth are suspicious for malignancy.
  • High-resolution ultrasound (HRUS) or contrast-enhanced ultrasound (CEUS) may show vascularity in malignant transformation.
  • MRI with contrast (DWI/ADC) can help distinguish benign from malignant polyps.

2. Gallbladder Adenoma

• Radiologic Features
  • Usually small (<1 cm), well-defined, homogenous hypoechoic lesions on ultrasound.
  • No invasion of the wall.
  • If growth is seen on follow-up imaging, malignancy should be suspected.

3. Gallbladder Dysplasia

• Radiologic Features
  • Often incidental and not directly visible on imaging.
  • May present as thickening of the gallbladder wall (>3 mm).
  • MRI and PET-CT may be useful for detecting early malignant changes.

4. Porcelain Gallbladder (Chronic Cholecystitis with Mural Calcification)

• Radiologic Features
  • CT: Characterized by curvilinear or diffuse calcification of the gallbladder wall.
  • Ultrasound: Echogenic wall with posterior acoustic shadowing.
  • Increased risk of gallbladder carcinoma, particularly if there is focal wall thickening.

5. Primary Sclerosing Cholangitis (PSC) and Chronic Inflammation

• Radiologic Features
  • Irregular gallbladder wall thickening.
  • Associated with hepatic and biliary duct abnormalities on MRCP.

6. Intracholecystic Papillary-Tubular Neoplasm (ICPN)

• Radiologic Features
  • Polypoid lesion protruding into the gallbladder lumen.
  • Well-defined lesion with cystic spaces on ultrasound and MRI.
  • May show enhancement on contrast imaging.

• Ultrasound: First-line for gallbladder evaluation.
• Contrast-Enhanced Ultrasound (CEUS): Helps differentiate benign from malignant polyps.
• CT/MRI: Useful for assessing gallbladder wall thickening and invasion.
• PET-CT: Can detect metabolically active malignant lesions.

• Gallbladder polyps >10 mm or showing rapid growth → Cholecystectomy recommended.
• Gallbladder wall thickening with suspicious features → Further imaging & biopsy.
• Porcelain gallbladder → Cholecystectomy due to cancer risk.

Gall bladder carcinoma: 

• T1a: Tumor invades lamina propria.
• T1b: Tumor invades the muscularis.
• Radiologic Findings:
  • Difficult to detect on imaging.
  • High-resolution ultrasound (HRUS): Focal wall thickening.
  • MRI/DWI: Subtle enhancement within the mucosal layer.
  • CT: May appear normal or show minimal thickening.

• T2a: On peritoneal side.
• T2b: On hepatic side.
• Radiologic Findings:
  • Ultrasound: Irregular focal or diffuse wall thickening.
  • CT/MRI:
    • Heterogeneous enhancement of the wall (better seen on MRI).
    • No extension into adjacent structures.
    • MRCP: May help in evaluating duct involvement.

• Radiologic Findings:
  • CT/MRI:
    • Heterogeneous enhancement with serosal disruption.
    • Direct invasion into the liver (segment IV/V most common).
    • Loss of fat planes with adjacent organs.
  • PET-CT: Detects metabolically active tumor spread.

• Radiologic Findings:
  • CT/MRI:
    • Encasement (>180° involvement) of the hepatic artery or portal vein.
    • Liver invasion beyond segment IV/V.
    • Invasion into multiple adjacent organs.
  • MR Angiography: Assesses vascular involvement.

• No suspicious lymph nodes on imaging.

• Radiologic Findings:
  • CT/MRI/US:
    • Enlarged nodes (>1 cm in short axis).
    • Round shape, irregular borders, central necrosis (suggestive of malignancy).
  • PET-CT: Hypermetabolic lymph nodes.

• Radiologic Findings:
  • Multiple large, necrotic, or conglomerated nodes.
  • Perivascular nodal involvement near SMA or celiac axis.
  • PET-CT: High sensitivity for nodal metastases.

• No signs of metastatic disease on imaging.

• Radiologic Findings:
  • Liver metastases:
    • Multiple hypodense or hypervascular lesions on CECT.
    • MRI (DWI) shows restricted diffusion.
  • Peritoneal metastases: Omental thickening, ascites, peritoneal nodules.
  • Lung metastases: Nodules on chest CT.
  • Bone metastases: Seen on PET-CT or bone scan.

1. Ultrasound (US)

   • First-line imaging for detecting gallbladder masses.
   • Can detect thickened walls, polyps, and masses.

2. Contrast-Enhanced CT (CECT)

   • Best for staging liver invasion and lymphadenopathy.
   • Identifies vascular involvement (hepatic artery, portal vein).

3. MRI/MRCP

   • Best for early-stage tumors (T1/T2) and biliary involvement.
   • DWI/ADC helps differentiate tumor from inflammatory changes.

4. PET-CT

   • Detects distant metastases and metabolic activity of lymph nodes.
   • Useful for M1 staging.

Subtle focal thickening, mild enhancement (MRI best). T2 Irregular thickening, perimuscular invasion (CT/MRI). T3 Serosal invasion, loss of fat planes with adjacent organs. T4 Vascular encasement, multi-organ involvement. N1 Regional lymphadenopathy (>1 cm, necrotic, round). N2 Distant nodal metastases (celiac, SMA, peripancreatic). M1 Liver, peritoneal, lung, or bone metastases (CT/MRI/PET-CT).