Carcinoma of the Colon

Risk Factors

• Adenomatous polyp
• Family history of benign or malignant colon tumors
• Chronic ulcerative colitis
• Crohn’s disease
• Prior pelvic radiation

• In women who have carcinoma of breast or uterine ca

• Retinitis pigmentosa
• Familial polyposis
• Gardener’s syndrome
• For synchronous lesions=1% (two or more colon ca’s at same time)
• For metachronous lesions=4-5% (likelihood of a person with colon ca developing 2nd)

Pathology

• Adenocarcinomas make up the vast majority
• Squamous cell carcinoma can start at the anal verge
• Cloacogenic carcinoma spreads mostly by direct invasion

Clinical Findings

• Peak age 50-70 years
• Weight loss
• Blood in stool
• Loss of appetite
• Change in  bowel habits  

Location

• Rectum (15%), sigmoid (20%), descending colon (10%), transverse colon (12%), ascending colon (8%), cecum (8%)
• Location seems to be changing and moving back to cecum
• More common in right colon with advancing years
• More common in left colon with chronic ulcerative colitis 

Imaging findings 

• 90-95% rate of detection by BE
• Polypoid filling defect
• Annular constricting=apple-core lesion
• Scirrhous ca-rare infiltrating type which gives lead-pipe appearance seen especially in ulcerative colitis
• Calcifications-rare
• May have retrograde without antegrade obstruction 

Mets to colon

• Stomach, breast, pancreas, and GU pelvic malignancies via blood
• May also spread via intraperitoneal seeding, especially from ovary 

Complications

• Obstruction-antegrade/retrograde or both
• Perforation is relatively common
• Carcinomas of the transverse colon can spread via direct extension to stomach
• Intussusception of lesions in TI or cecum
• Ischemic colitis may occur if chronic obstruction 

Metastases from Colon Cancer

• Liver (25%)
• Retroperitoneal and mesenteric nodes (15%)
• Hydronephrosis (13%)
• Adrenal (10%)
• Ovarian mets
• Ascites 

 
Colonic Carcinoma, Apple-Core Sign. An encircling mass in the mid-transverse colon (red arrow) mostly obstructs the retrograde flow of the barium in this single-contrast barium enema. The shelf-like defect caused by the distal end of the mass (white arrows) produces half of the "apple-core" sign of colon carcinoma.