Desmoplastic stroma and necrosis are complicating factors for iCCA biopsies and are associated with low tumor cell content, often reducing optimal yields for biomarker testing.40,41 In patients with refractory cancer with failed samples (n=61; failed samples had tumor cell content <30%), the presence of necrosis and fibrosis were both associated with biopsy failures (38% and 16%, respectively).42 In addition, mucin in stroma of liver metastases may contribute to poor tissue sampling.39 Here, MUC5AC is linked to neoplasm.