A Case of Colon Cancer Diagnosed as Lynch Syndrome Based on Clinicopathological Characteristics

Abstract

Lynch syndrome is caused by a germ-line mutation in a mismatch repair gene. It is an autosomal dominant hereditary disorder and increases the risk of developing colorectal cancer and various other types of cancers. Recently we have experienced a case of Lynch syndrome which could be diagnosed based on clinicopathological characteristics, though the patient lacked family history of cancer. The paper deals with the case with a review of the literature.
A 40-year-old man presented with positive reaction to the guaiac test was diagnosed with cancer of the cecum and transverse colon, and underwent extended right hemicolectomy with D3 dissection. Although he had no family members with cancer in the first degree, his neoplasms were of juvenile synchronous multiple colon cancers and revealed histological findings such as intra-tumorous infiltration of lymphocytes which are characteristic to colorectal cancers of highly unstable microsatellite instability (MSI-H). Accordingly, Lynch syndrome was suspected. On a MSI examination, it was identified as MSI-H. Immunostaining for mismatch repair protein resulted in lacks in MLH1 and PMS2. Genetic examinations after gene counseling disclosed germ-line mutation of MLH1. Lynch syndrome was finally diagnosed.