• mucinous biliary papillomatosis;
  • assessment of malignancy;
  • basement membrane discontinuities;
  • laminin

We report three cases of mucinous biliary papillomatosis occurring high in the extra-hepatic bile ducts. Histological assessment of malignancy is difficult and subjective because there is no unequivocal evidence of stromal invasion. Using anti-laminin antibodies to assess the basement membranes of these tumours we have found a large number of discontinuities in the epithelial basement membrane. On this basis we consider that mucinous biliary papillomatosis should be considered a low-grade malignancy. This would correlate with the natural history of these tumours, namely recurrence but with no widespread metastasis, death resulting from liver failure usually with 5–6 years of presentation.