Neoplastic lesions of Gastrointestinal Tract

Familial Polyposis Syndrome (FPS)

• Associated with a genetic defect in the APC gene
• Characterized by tubular adenomas with multiple osteomas, desmoid tumors, and epidermal cysts
• When the second allele of the APC gene is somatically mutated or lost by LOH, it leads to FPS

Genetic Defects and Colon Cancer

• The APC gene is associated with the genetic defect in FPS
• Mutations in the APC gene confer a growth advantage over neighboring cells in FPS
• Gene mutations associated with the chromosomal instability pathway in colon cancer include APC, beta-catenin, and others
• Defects in DNA mismatch repair genes lead to Lynch syndrome, a type of colon cancer
• The chromosomal instability pathway accounts for 85-90% of colon cancer cases

Characteristics of Polyps

• Juvenile polyps are characterized by a mixture of epithelial and stromal elements
• Peutz-Jeghers polyps are characterized by a treelike pattern of smooth muscle and a mixture of epithelial and stromal elements
• Polyps with melanotic pigmentation in mucocutaneous areas, lips, and perioral region are characteristic of Peutz-Jeghers syndrome

Syndromes and Colon Cancer

• Turcot syndrome is characterized by adenomas and CNS gliomas
• Hereditary Non-Polyposis Colorectal Cancer (HNPCC) is associated with a genetic defect in DNA mismatch repair genes

Precursor Lesions and Symptoms

• Adenomas are the precursor lesions of carcinoma in the gastrointestinal tract
• The most common symptom of right-sided colon carcinoma is anemia