The term tumour budding denotes that at the invasion front of colorectal adenocarcinomas tumour cells, singly or in small aggregates, become detached from the neoplastic glands. This morphological feature is increasingly being recognized as a strong and robust adverse prognostic factor. Biologically, tumour budding is closely related to the epithelial-mesenchymal transition. In this review the morphological features of tumour budding are discussed, as observed by the surgical pathologist reporting colorectal carcinoma resection specimens. The morphological features are put into context with the rapidly expanding knowledge of the epithelial-mesenchymal transition in general, and the molecular pathology of colorectal carcinoma in particular. Finally, a systematic analysis of the relevant published clinicopathological studies emphasizes the potential of tumour budding as a prognostic factor for routine surgical pathology.

This study confirms the prognostic value of budding in a contemporary series of colorectal carcinomas that by TNM were low risk. Technically easy, rapid and robust to determine, budding quantified in pan-cytokeratin stains significantly aids in the identification of high-risk patients and is recommended for more general use in surgical pathology.

CD66a, also called biliary glycoprotein (BGP), is a member of the carcinoembryonic antigen (CEA) family and of the immunoglobulin superfamily. CD66a is the human homologue of Cell-CAM, a well-defined cell adhesion molecule of the rat. In the present study a monoclonal antibody specific for CD66a was used to locate CD66a in human tissues. CD66a is expressed in epithelia, in certain endothelia, and in cells of the myeloid lineage. Hepatocytes were stained along the bile canaliculi. A characteristic apical membranous staining was observed in enterocytes, superficial absorptive cells of the colon, in the epithelia of esophageal and Brunner's glands, bile ducts and gallbladder, pancreatic ducts, proximal tubules of the kidney, prostate, endometrium, and mammary ducts. Selective staining of endothelia was present in glomeruli and vasa recta of the kidney, small placental vessels, adrenal sinusoids, endometrium, the prostate. Among the cells of the myeloid lineage, granulocytes and myelocytes were positive. The expression of CD66a by human cells and tissues is well comparable with the expression reported for Cell-CAM, the rat counterpart of CD66a. The wide tissue distribution of CD66a indicates that CD66a is a prominent human adhesion molecule.

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