06 Colon Polyps and Colon Cancers

The video takes a comprehensive look at colon polyps pathophysiology in preparation for the USMLE Step 1.

There are many types of colon polyps. Adenomatous in which there are two types. Villous (Villian) has a worse prognosis. Size the larger it is the more likely it is to be cancer and then there is dysplasia.

Symptoms: Rectal bleeding, obstruction, secretory diarhea and all of these have varying pathophysiology.

Juvenile Polyps: Malformation of the mucosa and usually happens in children who are less than 5 years old. Protrudes from the rectum and there is a syndrome called Juvenile Polyposis Syndrome. Pathophysiology: multiple juvenile polyps. THis is also associated with pulmonary Arteriovenous fistula

Hypoplastic Polyps - very common in the elderly 70-80. Dyspasia and these are generally benign as well.

Familial syndrome and their pathogenesis taht are associated with formation of colon polyps.

Puetz Jeghers are Autosomal Dominant. Multiple hamarotomatous polyps and you get a mucocutanoues pigmentation on the face. Complications: Intusseception (fatal) as well as some malignancies, such as breast, ovarian and other cancers.
Pathogenesis: it is linked iwth LKD1 and STK11 gene which causes it to decrease.

Familial Adenomatous Polyposis (FAP) found on chromosome 5p. THey have multiple polyps throughout the colon. THere are some variants:
Gardner - it is also associated osteomas, retinal hypertrophy, and also there is teeth in the mouth
Turcot - associated with CNS tumors, medulloblastoma, pheoblastoma.

Hereditary NonPolyposis Colon (HNPCC). Also autosomal dominant. Pathogenesis is problem in mismatch repair gene. Associated with MSH2 and MLH1. Increase Short Tandem Randoms.

Colon Cancer Pathogenesis
FAP model and HNPCC mdoel
FAP - mutation in APC then there is two hit. APC generally inhibit B-Catenin which is responsible for activated cyclin D1. Activates mutation of KRas and final hit of p-53

HNPCC model there is mismatch repair which leads to accumulation of gene factor

Risk factors is diet, low Vitamin A, C, K. Tobacco, Smoking, Inflammatory Bowel Disease, Puetz Jeghers, FAP, Villous adenoma for developing colon Cancer

Clinical Findings and Symptoms:
Iron Deficiency Anemia especially in ascending colon, which will be some sort of exophytic mass.
Colicky pain and hematochezia if found in descending colon. Mass will be more infiltrative inwards, not outwards.

Diagnosis
Iron Deficiency in elderly, you must rule out Colon cancer
Apple Core lesion on X-ray
CEA as tumor marking

• Category

  Familial Adenomatous Polyposis