Supplementary Material for: Hepatic progenitor cells in the form of ductular structures within a GIST liver metastasis: supporting a putative role in the hepatic metastatic niche

Recent studies have highlighted the presence of hepatic progenitor cells (HPCs) in metastatic liver carcinomas. We provide further evidence of this phenomenon, presenting a case of a gastrointestinal stromal tumour (GIST) liver metastasis with evidence of intra- and peritumoral HPC. A 64-year-old man presented with a gastric mass diagnosed as a high-risk KIT-mutated GIST. The patient was treated with Imatinib, recurring five years later with a liver mass. Liver biopsy disclosed a GIST metastasis, hallmarked by a proliferation of ductular structures without cytological atypia intermingled with the tumour cells, with a CK7/CK19/CD56-positive immunophenotype and rare CD44 positivity. The patient underwent liver resection, and the same ductular structures were present in the tumour interior and at its periphery. We document for the time the presence of HPC in the form of ductular structures in a GIST liver metastasis, further supporting their role in the liver metastatic niche.