Gallbladder metastasis is the spread of malignancies from other organs to the gallbladder and is rare. The most common sources are melanoma, breast carcinoma, lung carcinoma, renal cell carcinoma, and lymphoma/leukemia. Spread may occur via hematogenous, lymphatic, or direct invasion routes. Melanoma metastasis is the most common metastatic tumor of the gallbladder, with involvement detected in 15-20% of melanoma patients in autopsy series. On imaging, it may present as single or multiple polypoid intraluminal masses, focal or diffuse wall thickening, or intramural nodules. Differentiation from primary gallbladder carcinoma is made by clinical context (known malignancy history) and imaging features. When symptomatic, it may mimic acute cholecystitis.
Age Range
40-80
Peak Age
60
Gender
Equal
Prevalence
Rare
Gallbladder metastases develop through three main pathways. Hematogenous spread is the most common mechanism, particularly for melanoma — the high vascular tropism of melanoma cells and the gallbladder's rich arterial supply (cystic artery → portal circulation) facilitates hematogenous implantation. Melanin pigment in melanoma cells has T1-shortening effect (paramagnetic property) — therefore melanoma metastases show T1 hyperintense signal on MRI, a pathognomonic finding distinguishing them from other metastases. Lymphatic spread is more prominent for breast and lung carcinomas — reaching the gallbladder lymphatic network via hepatic hilar lymph nodes. Direct invasion occurs when liver metastases or adjacent colon/gastric tumors infiltrate the gallbladder wall. When metastatic tumor shows intraluminal polypoid growth, it appears on US as a hypoechoic or mixed echogenicity mass — unlike primary polyps, metastases are typically larger (>10 mm), may be multiple, and show increased vascularity.
Spontaneous T1 hyperintense signal of melanoma metastasis in the gallbladder — pathognomonic finding due to paramagnetic effect of melanin. Not seen in amelanotic melanoma. Known melanoma + T1 hyperintense gallbladder lesion strongly supports melanoma metastasis.
US shows single or multiple polypoid masses in the gallbladder lumen. Metastatic masses are usually >10 mm, broad-based or pedunculated, hypoechoic or mixed echogenicity. Melanoma metastases may contain hyperechoic components (melanin). The lesion does not move with position change (differentiation from gallstone). Multiple polypoid lesions strongly favor metastasis. Pericholecystic fluid is generally absent.
Report Sentence
A broad-based, hypoechoic polypoid lesion measuring approximately [x] mm in the gallbladder lumen without mobility; should be evaluated for metastasis in context of known malignancy.
Contrast-enhanced CT shows enhancing polypoid or nodular mass in the gallbladder lumen. Hypervascular metastases (melanoma, RCC, neuroendocrine) enhance intensely in arterial phase. Melanoma metastases may show high density on non-contrast CT (melanin). Enhancement persists in portal venous phase. The mass is clearly delineated from bile (0-20 HU). Concurrent liver metastases are frequently present.
Report Sentence
An intensely arterially enhancing polypoid mass measuring approximately [x] mm is seen in the gallbladder lumen; hypervascular metastasis should be primarily considered in context of known malignancy.
On MRI, melanoma metastases show hyperintense signal on T1-weighted sequences — pathognomonic finding due to paramagnetic effect of melanin pigment. Variable T2 signal (intermediate-low). In amelanotic melanoma, T1 hyperintensity is absent. Avid enhancement on post-contrast series. Diffusion restriction (low ADC) on DWI reflects tumoral cellularity.
Report Sentence
Polypoid lesion with hyperintense T1 signal in the gallbladder lumen, consistent with melanoma metastasis.
Doppler US demonstrates internal vascularity (arterial flow) in metastatic masses. Cholesterol polyps are avascular with no Doppler signal — this distinction is critical. Metastatic masses show irregular, increased internal and peripheral vascularity. Low resistance index (RI <0.5) supports tumoral neovascularity.
Report Sentence
Internal vascularity demonstrated on Doppler US in the gallbladder lesion; avascular cholesterol polyp excluded.
Some metastases present as diffuse or focal irregular wall thickening. Wall thickness >5 mm, irregularly contoured with heterogeneous enhancement. This pattern is more frequent in breast and lung metastases. Lymphomatous involvement can also produce similar diffuse wall thickening. Pericholecystic fat infiltration is variable — absence helps differentiate from acute cholecystitis.
Report Sentence
Diffuse, irregular gallbladder wall thickening with heterogeneous enhancement; metastatic involvement should be evaluated in context of known malignancy.
PET-CT shows increased FDG uptake (SUVmax >3-4) supporting metastatic involvement. Melanoma, lung carcinoma, and lymphoma metastases show high FDG avidity. Dual time-point imaging helps differentiate from physiologic biliary activity — SUV increases in tumoral lesions while physiologic activity decreases.
Report Sentence
Increased FDG uptake (SUVmax: [x]) in the gallbladder lesion, favoring metastatic involvement.
Metastatic lesions show significant diffusion restriction on DWI — hyperintense at high b-values, hypointense on ADC map. ADC usually <1.2 × 10⁻³ mm²/s. Helps differentiate from benign polyps (high ADC) and bile (very high ADC). T1 hyperintensity + diffusion restriction in melanoma increases diagnostic confidence.
Report Sentence
Significant diffusion restriction in the gallbladder lesion on DWI, favoring tumoral cellularity.
Criteria
Most common metastatic tumor of gallbladder. Hematogenous spread. 15-20% involvement in autopsy series. T1 hyperintense signal is pathognomonic. Polypoid intraluminal mass. Hypervascular.
Distinct Features
May be multiple. High density on non-contrast CT due to melanin. No T1 hyperintensity in amelanotic variant. Tropism related to rich vascular network.
Criteria
Hematogenous spread. Hypervascular — intense arterial enhancement. May present as late metastasis (years after nephrectomy). Clear cell RCC most commonly metastasizes to gallbladder.
Distinct Features
Similar vascular pattern to melanoma metastasis. Slightly high density on non-contrast CT (possible hemorrhage). High T2 signal (clear cell variant). Polypoid or mural nodule.
Criteria
Hematogenous or lymphatic spread. Diffuse wall thickening pattern is more common. Invasive lobular carcinoma causes diffuse thickening due to infiltrative growth.
Distinct Features
Concurrent liver metastases common. May be seen with peritoneal carcinomatosis. Wall thickening may mimic cholecystitis — clinical correlation critical.
Criteria
Non-Hodgkin lymphoma more common. Diffuse wall thickening predominant — homogeneous, hypodense infiltration. Usually in widespread disease context.
Distinct Features
Low-to-moderate enhancement (hypovascular). Very low ADC on DWI. High FDG uptake on PET-CT. Splenomegaly and diffuse LAP may accompany.
Distinguishing Feature
Primary carcinoma typically develops in women 60+, on gallstone background. Direct liver bed invasion is characteristic of primary carcinoma. Metastasis is expected with known primary malignancy and other organ metastases.
Distinguishing Feature
Cholesterol polyps <10 mm, multiple, bright hyperechoic, avascular. Metastasis >10 mm, mixed echogenicity, with internal vascularity.
Distinguishing Feature
Acute cholecystitis: diffuse wall thickening + pericholecystic fluid + Murphy sign + gallstones. Metastatic thickening: no pericholecystic fluid or Murphy sign.
Distinguishing Feature
Adenomyomatosis: Rokitansky-Aschoff sinuses (comet-tail artifact, 'pearl necklace' sign). These findings are absent in metastasis.
Urgency
urgentManagement
surgicalBiopsy
NeededFollow-up
specialist-referralGallbladder metastasis indicates widespread disease, generally stage IV. Management determined by primary tumor type. Cholecystectomy may be needed symptomatically but is palliative. Histological confirmation important for differentiating from primary carcinoma.
Gallbladder metastasis indicates systemic metastatic disease. Treatment depends on the stage and extent of the underlying malignancy. Cholecystectomy may be considered for isolated gallbladder metastasis. Evaluation of the gallbladder is important in melanoma patients.