Comparing Clinicopathological and Immunohistochemical Features of Colorectal Carcinoma between Young and Old Age Groups.

The incidence of colorectal carcinoma (CRC) is increasing among individuals younger than 50, and some studies suggest the presence of differences in CRC among old and young individuals regarding clinical and histopathological features. The aim of this study was to compare clinicopathological features, mismatch repair protein status, and expression of certain immunohistochemical stains between young and old groups. The study included 180 cases and found significant histological and immunohistochemical differences between the two groups. CRC in the young tends to be more right-sided and has a higher percentage of dMMR proteins, but less expression of p53 mutations. These features are commoner in Lynch syndrome, and more investigations to study the relationship between young-onset CRC and hereditary syndromes are needed. Young-onset CRC also tends to show higher expression of tumor cell PD-L1, which is an expected finding, as dMMR cases are more likely to be immunogenic. Two other significant differences are the higher percentage of mucinous carcinoma and the higher tumor grade in young-onset CRC. These two features suggest a more advanced disease with possibly worse outcomes; however, there is no difference in disease stage between the two age groups.