Histologic features distinguish microsatellite-high from
microsatellite-low and microsatellite-stable colorectal
carcinomas, but do not differentiate germline mutations
from methylation of the
Martha Yearsley MD
, Heather Hampel MS
, Amy Lehman MAS
Hidewaki Nakagawa MD, PhD
, Albert de la Chapelle MD, PhD
, Wendy L. Frankel MD
Department of Pathology, The Ohio State University Medical Center, Columbus, OH 43210, USA
Division of Human Cancer Genetics Comprehensive Cancer Center, The Ohio State University, Columbus, OH 43210, USA
Center for Biostatistics, The Ohio State University College of Public Health, Columbus, OH 43210, USA
Received 2 August 2005; revised 30 January 2006; accepted 2 February 2006
Summary The detection of microsatellite-unstable (microsatellite instability [MSI]) colorectal carcinomas
(CRCs) has prognostic value and can help screen for Lynch syndrome. We determined which histologic
features are associated with MSI status and presence of germline mutation and/or methylation of MLH1
promoter. Patients diagnosed with CRC were offered participation in the Columbus-area hereditary
nonpolyposis colorectal cancer syndrome study regardless of age or family history. Tumors were
evaluated for MSI using a modified Bethesda panel of microsatellite markers. Methylation status of the
MLH1 promoter was evaluated by methylation-specific polymerase chain reaction and bisulfite PCR
followed by restriction digestion of tumor DNA. All patients with microsatellite-unstable tumors
underwent mutation analysis of the MLH1, MSH2, and MSH6 genes by full sequencing of genomic DNA
and by multiplex ligation probe assay of MLH1 and MSH2. Histologic end points were tumor type, grade,
percentage of mucin, border, and lymphoid host response. Of the 482 CRCs, 87 were MSI with 69 MSI
high (MSI-H), 18 MSI low (MSI-L), and 395 microsatellite stable (MSS). Of 87 MSI tumors, 12 had
germline mutations and 34 had methylation of the MLH1 promoter. Younger age, but not histologic
features, was significantly associated with a germline mutation. Percentage of mucin, histologic type,
grade, and lymphoid host response differed significantly between MSI-H when compared with MSI-L or
MSS. No difference was found between MSI-L versus MSS. Histologic features are associated with
MSI-H CRC and are helpful to differentiate MSI-H from MSI-L and MSS. These features are not useful to
distinguish MSI-L from MSS carcinomas, and those with a deleterious germline hereditary nonpolyposis
colorectal cancer syndrome mutation from those with methylation of the MLH1 promoter region.
D 2006 Elsevier Inc. All rights reserved.
0046-8177/$ – see front matter D 2006 Elsevier Inc. All rights reserved.
This study was supported by grants CA16058 and CA67941 from the National Institutes of Health.
* Corresponding author.
E-mail address: firstname.lastname@example.org (W. L. Frankel).
Human Pathology (2006) 37, 831 – 838