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Tumor Discovery Unusual cause of biliary obstruction

metastasis occurring in 3% of cases. Case reports and cancer that determine its risk of progression. In this case,
12
2
small case series suggest that MBTO secondary to UC although the patient did not report urinary symptoms,
accounts for <1% of all MBTOs, which are most commonly the positive staining for p40, p63, high-molecular-weight
caused by pancreatic, cholangiocarcinoma, or metastatic keratin, and GATA-3 in the tissues strongly indicates
colorectal cancers. 3 a urothelial origin. Therefore, further investigation for

Initial diagnosis involves distinguishing between primary urothelial cancer should be the next step.
benign and malignant conditions, often achieved through The most prevalent bladder tumor histologies include
magnetic resonance cholangiopancreatography (MRCP) UC, characterized by invasion into the muscularis propria
or ERCP. Both MRCP and ERCP are preferred over CT and representing the majority of cases in the US and
scans due to their higher sensitivity and specificity, with Europe. Squamous cell carcinomas, originating from the
85% and 71% for MRCP and sensitivity of 75% for ERCP, urothelium, constitute a small percentage of cases, while
respectively. Recent studies have shown that MRCP’s adenocarcinomas, exhibiting a glandular phenotype, are
3,4
sensitivity exceeds 96% and specificity reaches 85% for rarer still, typically arising from the bladder’s urothelium
differentiating between benign and MBTOs. In addition, or remnants of the urachus. 13,14
2,4
ERCP’s diagnostic accuracy is enhanced by adjunct
techniques such as EUS and intraductal ultrasound. 5 This case underscores the importance of considering
distant metastases, particularly from bladder cancer, in
Metastatic UC to the liver typically demonstrates the differential diagnosis of MBTO and emphasizes the
hypovascularity on contrast-enhanced CT, with minimal significance of comprehensive diagnostic approaches
arterial enhancement and progressive enhancement and multidisciplinary collaboration for optimal patient
during the portal venous and delayed phases. On MRI, management.
lesions appear hypointense on T1-weighted images, mildly
hyperintense on T2-weighted images, and exhibit restricted 4. Conclusion
diffusion on diffusion-weighted imaging sequences, MBTO is a common presentation of hepato-pancreato-
with delayed progressive contrast enhancement. Unlike biliary cancer. However, a distant metastasis could mimic
hypervascular metastases from neuroendocrine tumors
or renal cell carcinoma, urothelial metastases lack early the presentation. Gastrointestinal workup with ERCP and
arterial phase enhancement. On EUS, they present as EUS for tissue sampling or cytology has low yield in terms
hypoechoic, stiff, and hypovascular lesions, consistent with of diagnosing MBTO. Even if the result is negative, further
other adenocarcinoma metastases. 6-9 workup of tissue biopsy should be done for the definitive
diagnosis. If metastasis is suspected, investigations for
When malignancy is suspected, tissue sampling primary cancer based on pathology results should be the
becomes crucial to refine the diagnosis. Brush cytology next step.
coupled with forceps or needle biopsy is recommended
over brush cytology alone due to its increased sensitivity Acknowledgments
and specificity. While brush cytology typically exhibits The authors would like to thank the Department of
sensitivity rates around or below 50%, its specificity Pathology, Texas Tech University Health Sciences Center
remains notably high at 95%. Forceps or needle biopsy
10
can further elevate sensitivity to 70% and specificity (TTUHSC), for providing the original pathology images
to 100%, respectively. Percutaneous transhepatic used in this manuscript. In addition, we extend our
10
cholangiography serves as a secondary diagnostic option gratitude to Nutthamon Aroonwon for her assistance in
when ERCP is unsuccessful or infeasible and the patient editing and formatting the figures.
2
has potential bleeding complications. In our case, while Funding
the EUS and brush biopsy yielded negative results,
the clinical presentation strongly suggested cancer, None.
necessitating a pathology diagnosis to guide appropriate
treatment. Consequently, a liver biopsy was performed as Conflict of interest
the next step. The authors declare they have no competing interests.
In addition, positive tumor markers can help diagnose Author contributions
UC. Some tumor markers with high sensitivities (>75%)
for UC include uroplakin II, p40, p63, GATA 3, and Conceptualization: Sakditad Saowapa, Chalothorn
CK903. 11-13 In addition, there are a variety of histological Wannaphut
variants, subtypes, and immunophenotypes of urothelial Formal analysis: Natchaya Polpichai, Pharit Siladech

Volume 4 Issue 3 (2025) 98 doi: 10.36922/TD025070011