Pterygia have been reported to share some of the genetic defects seen in cancers, including microsatellite instability (MSI). We examined pterygia for the presence of proteins typically missing or defective in adenocarcinomas with MSI. We also performed microsatellite analysis on DNA from pterygia to test for instability in the size of the microsatellites, using markers conventionally used to characterize MSI in tumors (Bethesda convention markers).
We examined 13 pterygia by immunohistochemistry for MLH1 and MSH2, 2 proteins involved in DNA mismatch repair. In addition, we amplified the pterygial DNA with primers specific for 5 Bethesda markers (BAT25, BAT26, D2S123, D5S346, and D17S250).
MLH1 staining was present at low levels in the basal cells of the cornea and migrating limbal cells of the pterygia. MSH2 staining was present in basal and in maturing epithelial cells of the cornea and migrating limbal cells of pterygia. We observed no reproducible examples of MSI or loss of heterozygosity (LOH).
We were unable to confirm the presence of MSI and LOH by using the markers we examined. MSH2 staining appeared to be normal in pterygia. MLH1 staining was present but in reduced amounts compared with that seen in the conjunctiva.
From the *Division of Gastroenterology, Department of Medicine, Vanderbilt University School of Medicine, Nashville, TN; †Columbia University College of Physicians and Surgeons, New York, NY; ‡Louisiana State University Health Sciences Center, New Orleans, LA; §Kaiser Permanente Medical Center, Sacramento, CA; and ¶Texas Tech University Health Sciences Center, Lubbock, TX.
Received for publication September 26, 2006; revision received November 10, 2006; accepted December 2, 2006.
Supported by Kaiser Foundation Research Institute Grant 61-9783, the Health Excellence Fund of the Board of Regents of the State of Louisiana, and National Cancer Institute Grant R25CA082351.
Reprints: Barbara G. Schneider, Division of Gastroenterology, Department of Medicine, 1030-C MRB4, Vanderbilt University School of Medicine, 2215 Garland Avenue, Nashville, TN 37232 (e-mail: email@example.com).