NCAM1 and bile duct papillary neoplasm: Further, CD20+ B lymphocytes and MUM1+ plasma cells were rarely found in the intraepithelial compartment of IPN cases (3.1%, n = 2/65 and 4.6%, n = 3/65, respectively), intraepithelial CD68+ macrophages were identified in over 64% (n = 42/65) of the analysed IPN tissue and no intraepithelial CD56+ NK cell infiltration was observed (Fig. 3a).