Hamartomatous polyps occursporadicallyorasapartofgeneticdiseases.Inthelattercase,theyoftenareassociatedwithincreasedriskformalignancy.
Hyperplastic polyps arebenignepithelialproliferationsmostcommonlyfoundintheleftcolonandrectum.Theyarenotreactiveinorigin,incontrastwithgastrichyperplasticpolyps;havenomalignantpotential;andmustbedistinguishedfromsessileserratedadenomasorpolyps.
Benign epithelial neoplastic polyps ofthecolonaretermedadeno-mas.Thehallmarkfeatureoftheselesions,whicharetheprecursorsofcolonicadenocarcinomas,iscytologicdysplasia.
Incontrastwithtraditionaladenomas,sessile serrated adenomas,orpolyps,lackcytologicdysplasiaandsharesomemorphologicfeatureswithhyperplasticpolyps.
Familial adenomatous polyposis (FAP) andhereditary nonpolyposis colorectal cancer (HNPCC) arethemostcommonformsoffamilialcoloncancer.FAPiscausedbyAPC mutations,andpatientstypicallyhaveover100adenomasanddevelopcoloncancerbefore30yearsofage.
HNPCCiscausedbymutationsinDNAmismatchrepairgenes.PatientswithHNPCChavefarfewerpolypsanddevelopcanceratanolderagethanthattypicalforpatientswithFAPbutatayoungeragethaninpatientswithsporadiccoloncancer.
Thevastmajorityofcoloniccancersareadenocarcinomas.TheyariseeitherbyAPC-β-cateninpathwayorthemicrosatelliteinstabilitypathway.Thetwomostimportantprognosticfactorsaredepthofinvasionandthepresenceorabsenceofmetastasestolymphnodesordistantorgans.
The appendix is a normal true diverticulum of the cecum. Like any diverticulum, it is prone to acute and chronic inflammation, and acute appendicitis is a relatively common entity. Other lesions, including tumors, can also occur in the appendix but are far less common.
Acute appendicitis is most common in adolescents and young adults but may occur in any age group. The lifetime risk for appendicitis is 7%; males are affected slightly more often than females. Despite the prevalence of acute appendicitis, the diagnosis can be difficult to confirm preoperatively, and the condition may be confused with mesenteric lymphadenitis, acute salpingitis, ectopic pregnancy, mittelschmerz (pain associated with ovulation), and Meckel diverticulitis.
Acute appendicitis is thought to be initiated by progressive increase in intraluminal pressure that compromises venous outflow. In 50% to 80% of cases, acute appendicitis is associated with overt luminal obstruction, usually by a small, stone-like mass of stool, or fecalith, or, less commonly, a gallstone, tumor, or mass of worms. Ischemic injury and stasis of luminal contents, which favor bacterial proliferation, trigger inflammatory responses including tissue edema and neutrophilic infiltration of the lumen, muscular wall, and periappendiceal soft tissues.