This hypothesis is reinforced by the highly significant association of CK7 expression between tumour tissue and respective mucosa, an association lacking in no-PID-SBC cases, as well as by the occasional finding of direct topographic continuity between CK7 and/or MUC5AC-positive mucosal lesions and the invasive cancers of the same phenotype, which we identified in some CrD-SBC cases. This evidence concerns the gene MUC5AC and neoplasm.