Abstract

BACKGROUND
High microsatellite instability (MSI-H) colorectal carcinomas (CRCs) with numerous mutations in the microsatellite sequence are characterized by a right-sided preponderance, frequent peritumoral and intratumoral lymphocytic infiltration, and frequent mucin production. However, no study has correlated anatomic site and type of genetic changes with clinicopathologic changes.
METHODS
We analyzed the histopathologic features of 135 MSI-H CRCs and compared them to 140 microsatellite stable (MSS) CRCs. Histopathologic changes in MSI-H were further analyzed according to anatomic sites and genetic changes.
RESULTS
MSI-H CRCs showed previously reported clinicopathologic findings; a right-sided preponderance, an increased number of mucinous carcinomas, and peritumoral lymphoid reactions (p<0.001 for each variable). Increased serum CEA levels showed an MSS CRC preponderance (p=0.013). We further analyzed the histologic differences between right- and left-sided MSI-H tumors. We found that MSI-H CRCs on both sides had similar clinicopathologic findings, except for higher tumor stage (p=0.048) and less frequent abnormal CEA levels in left-sided MSI-H tumors (p=0.027). We found that not all clinicopathologic features were different between hereditary nonpolyposis colorectal cancers (HNPCCs) and sporadic MSI-H CRCs.
CONCLUSIONS
These findings indicate that MSI-H CRCs of the left colon have similar clinicopathologic characteristics as right-sided MSI-H CRCs. We did not find any significant clinicopathological difference between HNPCCs and sporadic MSI-H CRCs.

• Keywords: Colorectal neoplasm;Microsatellite instability;Colorectal neoplasms, hereditary nonpolyposis;