Hepatic progenitor cells in metastatic liver carcinomas.

AIMS: Hepatic progenitor cells (HPCs) are activated in various liver diseases, but their role in the carcinomatous environment remains unknown. We aimed to identify the possible presence and topography of HPCs in liver metastases.

METHODS AND RESULTS: We examined 14 liver resection specimens for colorectal adenocarcinoma (n = 13) and anal squamous cell carcinoma (n = 1) metastases. Immunohistochemical markers of colonic origin (keratin 20 and CDX2) and squamous cell origin (p63), HPC [keratin 19 (K19) and CD56] and stem cell (CD44) markers, and the biliary marker keratin 7 (K7), which may also highlight HPCs, were applied on routinely processed tissue sections. Double immunohistochemistry/immunofluorescence (K7/CDX2) and confocal microscopy were used on selected sections. K7-positive, Κ19-positive and CD56-positive ductular structures were encountered within the metastatic tumour (tumour interior and periphery), and in the immediate peritumoral area. Hybrid structures composed of HPCs and metastatic adenocarcinoma cells were recognised and confirmed by double immunostaining (K7/CDX2). Carcinoma cells were also observed singly or in groups within the epithelium of interlobular bile ducts and/or ductules in portal tracts without evidence of carcinomatous infiltration and at a distance from the metastatic foci.

CONCLUSIONS: HPCs are observed at the periphery and in the interior of liver metastatic carcinomas. Bile ductules and small interlobular bile ducts may attract carcinoma cells serving as a potential 'metastatic niche', in line with their recognised role as HPC niches in non-neoplastic liver.