This document discusses colorectal cancer (CRC) and provides information on Lynch syndrome (LS) and familial colorectal cancer type X. It covers the classification, pathogenesis, clinical features, and investigations of CRC. It also compares LS to sporadic CRC and notes that LS is genetic, presents at a younger age with more synchronous and metachronous tumors that are often proximal and mucinous or poorly differentiated. The diagnosis can be difficult as the spectrum of polyposis and genetics are vast.

1. Dr. (Maj) Ajay Kandpal
MD MEDICINE, DNB MEDICINE
DM PG (Gastro enterology) STANLEY MEDICAL COLLEGE
CHENNAI, INDIA
kandykilroy@gmail.com

2.  Introduction
 Classification of CRC
 Polyposis vs non-polyposis syndrome
 Pathogenesis
 Clinical features
 Investigations
 Mgt

10.  Familial colorectal cancer type X
◦ Amsterdam Criteria-1 (AC1) for Lynch syndrome
(LS), but whose tumours are DNA-mismatch-repair-
proficient
 LS like syndrome

12. LS FCCTX
Location Proximal distal
Pathology Mucinous CA Less common
Invasion Less common Venous invasion

14. Eg. chromosome
Protooncgene K-ras 12
Tumor suppressor APC
DCC
SMAD4
5
18
18
DNA mismatch repair HMLH1
HMSH2
HMSH6
3
2
2

23. LYNCH SYDROME SPORADIC CRC
Genetics Yes No
Risk factors No Yes
Mean age 45 65
Multiple/synchronous/
metachronous
35/20/25 4/3/1
Location Proximal 30
Malignant tumors at
other site
Yes No
Microscopic pathology Mucinous and poorly
differentiated
Less common
Prognosis fair variable

27.  Difficult
 Vast spectrum of polyposis
 Only definitive is genetics