Medicosis Perfect Med's Review: Lynch Syndrome

Introduction

• Medicosis Perfect Med is a resource where complex medical topics are broken down.
• Previous topics covered:
  • Nephritic Syndrome
  • Nephrotic Syndrome
  • Amniotic Fluid Embolism
  • Barrett Esophagus
  • Familial Adenomatous Polyposis
• Current topic: Lynch Syndrome

Lynch Syndrome Overview

• Also known as Hereditary Non-Polyposis Colorectal Cancer (HNPCC)
• Unlike Familial Adenomatous Polyposis (FAP), it involves no polyps
• Can lead to colon cancer and other types of cancers

Cancer Basics

• Cancer is a neoplasia, which can be benign or malignant
  • Benign: Adenoma
  • Malignant: Adenocarcinoma
• Tumors can be:
  • Carcinomas (epithelial cancers)
  • Sarcomas (connective tissue cancers)
• Cancers can metastasize via lymph or blood

Characteristics of Cancer Growth

• Growth exceeds normal tissue growth
• Uncoordinated with normal tissue
• Continues even after stimulus stops
• Risk factors, not causes (correlation ≠ causation)
• Can be functioning (secreting) or non-functioning (non-secreting)

Types of Stools and Indications

• Normal Stool: Brown
• Pale/Clay Stool: Seen in obstructive jaundice
• Steatorrhea: Greasy/oily stool indicates malabsorption
  • Loss of fat-soluble vitamins (K, E, D, A)
• Black Stool (Melena): Upper GI bleed
• Bright Red Stool: Lower GI bleed or right-side colon cancer

Polyps and Colorectal Conditions

• Polyps are usually non-malignant
• Malignant polyps: adenomatous, villous, serrated
• FAP: Thousands of polyps, near certain progression to cancer
  • Autosomal dominant
  • Mutation in tumor suppressor gene (APC on chromosome 5)
  • Associated with Turcot syndrome (brain tumors) and Gardner syndrome (variety of tumors)

Lynch Syndrome Specifics

• Autosomal dominant
• No polyps
• More common but less severe than FAP
  • 80% develop colon cancer vs. 100% in FAP
• DNA mismatch repair issue leading to microsatellite instability
  • Genes involved: MLH1, MSH2
• Associated with other cancers: endometrial, ovarian, skin

Management of Colorectal Cancer

• Early Stage: Surgical removal
• Advanced Stage: Chemotherapy (e.g., FOLFOX, FOLFIRI)

Summary of Key Differences

• FAP:
  • Mutation in APC gene
  • 100% chance of colorectal cancer
  • Begins after puberty
  • Associated with Turcot and Gardner syndromes
• Lynch Syndrome:
  • DNA repair failure
  • 80% chance of colorectal cancer
  • Associated with multiple non-colorectal cancers

Additional Resources

• Videos on hereditary cancer syndromes
• Pathology playlist on cancer basics
• Courses on various cancers and surgery high yields available

Closing Remarks

• Subscribe for more content
• Visit Medicosis for courses and resources
• Stay safe and study hard