Bile Duct Colonization by Metastatic Tumor: A Potential Mimic of Cholangiocarcinoma
ML Othman, SC Abraham. MD Anderson Cancer Center, Houston
Background: Distinction between primary and metastatic carcinoma in the liver has important therapeutic implications. The presence of an "in situ" intraductal growth pattern is often taken as evidence of primary cholangiocarcinoma (CCA), but metastatic colorectal carcinoma (CRC) can occasionally exhibit colonization of biliary epithelium and thereby mimic CCA. The frequency of this pattern and its occurrence with other metastatic tumors are unknown.
Design: We reviewed diagnostic reports and gross descriptions of all liver resections for metastatic tumor between 1997-2009 to identify cases with any suggestion of bile duct involvement. Histologic sections were scored for the following: extent of intrabiliary growth, colonization of biliary epithelium, size of largest involved duct, and duct obstructive histology in non-neoplastic parenchyma. Radiologic findings and liver chemistries were obtained from the computerized medical records.
Results: There were 1072 hepatic resections for CRC and 425 for other metastases (Table 1). Intrabiliary growth was present in 35 (3.3%) CRCs, and colonized biliary epithelium in an apparent "in situ" growth pattern in 28 (85%) of 33 cases with available histologic sections. Intrabiliary growth was focal in 14 (40%) and prominent in 21 (60%); 3 of the latter had predominant intrabiliary tumor with very little stromal invasion. Four cases radiologically mimicked CCA. In contrast to CRC, only 3 (0.7%) of the other 425 metastatic tumors showed intrabiliary growth (p=0.003) (pancreatic endocrine carcinoma, breast carcinoma, and GIST; both breast and endocrine tumors also colonized biliary epithelium).
Conclusions: At least 3% of metastatic CRCs show intrabiliary growth and some have extensive colonization of biliary epithelium that can mimic CCA. Intrabiliary growth and epithelial colonization can also occur with other metastases, but this is significantly less common (p=0.003) and should not pose a diagnostic dilemma. In patients with a history of CRC, apparent "in situ" intrabiliary growth does not negate a metastatic diagnosis.
|Metastatic tumor||Intrabiliary growth||Colonization of biliary epithelium||Largest involved duct (mean, range)||Obstructive changes in peripheral liver||Biliary abnormalities by radiology||Alkaline phosphatase elevation|
|CRC (n=1072)||35 (3.3%)||28 of 33 (85%)||0.4 cm (0.01-2.0)||18 of 32 (56%)||18 of 35 (51%)||16 of 35 (46%)|
|Other (n=425)*||3 (0.7%)||2 of 3 (67%)||0.8 cm (0.02-1.5)||0 of 2 (0%)||1 of 3 (33%)||1 of 3 (33%)|