Similar to the men, the decline among women is believed to reflect the success of early detection, treatment, and, possibly, changing dietary and lifestyle factors. The similar decline in CRC mortality among both men and women suggests that screening with FOBT and, perhaps, flexible sigmoidoscopy has been effective. Most CRCs arise within benign adenomas. Malignant transformation of these benign lesions into adenocarcinoma depends on the size, histology, and degree of epithelial dysplasia of the adenoma. The progression is further determined by accumulated genetic alterations.
Most adenocarcinomas form hard, nodular areas that grow irregularly.
Histologically, CRC may form varying cells from well-differentiated cells that appear normal to aggressive anaplastic cells that may contain a variable amount of mucin. 8 Table 2 reviews the more simplified Dukes' classification. The depth of CRC invasion can be staged using Dukes' classification or a modified Dukes' classification. Approximately one third of CRC patients will present with clinical evidence of metastatic disease. This was followed in frequency by weight loss, rectal bleeding, nausea and vomiting, constipation, and narrow caliber stools.