Colorectal polyps and carcinoma: Role of the pathologist

Colorectal carcinoma is the third most common cancer in the United States in both men and women, and subsequently it is also the third leading cause of cancer-related death in the United States. In the era of personalized medicine, gastroenterologists, colorectal surgeons, oncologists and medical geneticists have started depending on the pathologist’s consultation in the management of patients with colorectal polyps or carcinoma. The pathologist’s role is not restricted to mere histomorphologic subtyping but is greatly expanding to provide accurate pathologic stage, analysis of surgical resection margins, identification of prognostic parameters that are not included in the staging such as lymph-vascular and perineural invasion, tumor budding, and assessment of therapeutic effect in patients who have received neoadjuvant therapy. With the rapid therapeutic advancement in available therapeutic options, pathologists also play a leading role in assessing mismatch repair protein expression, selecting appropriate tissue sections for microsatellite instability testing and KRAS, NRAS, BRAF, and PIK3CA mutation analysis, and in interpreting the results of these important therapeutic and prognostic tests. This chapter focuses in the role of the pathologist evaluating preneoplastic lesions, malignant polyps and familial polyposis as well as colorectal carcinoma and its predictor and prognostic factors.