Malignant epithelial neoplasms of the large intestine

Adenocarcinomas of the large bowel are among the most common human malignancies. This chapter discusses the epidemiology and pathogenesis of large-bowel cancer. It reviews aspects of epidemiology, biology, pathology and modern therapy that will provide a richer understanding of the context in which a particular specimen is interpreted. The chapter also discusses the concepts arising from the inherited pathways, allowing the introduction of specific molecular genetic data relevant to sporadic pathways. The aetiology of colorectal cancer encompasses both environmental and endogenous influences. Colorectal carcinoma may begin with the inheritance of a mutated tumour suppressor gene, as with familial adenomatous polyposis and Lynch syndrome. Small-cell and large-cell undifferentiated carcinoma may be placed at the most malignant end of the neuroendocrine spectrum. Microscopic grading of colorectal cancer has long been part of routine pathology practice. Glandular architecture is obvious in most colorectal cancer and is characteristic of well-differentiated and moderately differentiated neoplasms.