Low-level microsatellite instability colorectal carcinomas: do they really belong to a "gray zone" between high-level microsatellite instability and microsatellite-stable cancers?
OBJECTIVE
Colorectal carcinomas demonstrating low-level microsatellite instability (MSI-L) may form a distinct group differing both from high-level MSI (MSI-H) and microsatellite-stable (MSS) tumors.


METHODS
In a retrospective series of 172 colorectal carcinomas the microsatellite status was examined based on DNA extracted from archival blocks. Three groups - MSS ( n=100), MSI-L ( n=37), MSI-H ( n=35) - were compared with respect to clinical data, stage, histology, and immunoexpression of Ki-67, and P53.


RESULTS
Compared to MSS and MSI-H carcinomas the MSI-L tumors were exceptionally rarely right-sided, and demonstrated the lowest proliferation fraction. There was a trend for less frequent high-grade histology, more frequent intermediate P53 expression, and prominent mucinous histology.


CONCLUSIONS
Features of MSI-L colorectal carcinomas are not necessarily located between their MSS and MSI-H counterparts. The MSI-L category may contain a group of tumors belonging to a distinct carcinogenetic pathway.
Rudzki
Zbigniew
Z
Department of Clinical and Experimental Pathomorphology, Collegium Medicum, Jagiellonian University, Grzegórzecka 16, 30-124 Cracow, Poland. mprudzki@cyf-kr.edu.pl
Zazula
Monika
M
Okoń
Krzysztof
K
Stachura
Jerzy
J
D002277:Carcinoma / Q000235:genetics* / Q000378:metabolism / Q000473:pathology; D015179:Colorectal Neoplasms / Q000235:genetics* / Q000378:metabolism / Q000473:pathology; D004273:DNA, Neoplasm / Q000032:analysis; D005260:Female; D006801:Humans; D019394:Ki-67 Antigen / Q000378:metabolism; D008297:Male; D018895:Microsatellite Repeats; D008875:Middle Aged; D012189:Retrospective Studies; D016159:Tumor Suppressor Protein p53 / Q000378:metabolism
D004273:DNA, Neoplasm; D019394:Ki-67 Antigen; D016159:Tumor Suppressor Protein p53