Abstract
Objectives
Microsatellite instability (MSI) is a type of genetic instability due to errors in the mismatch repair system. In the respiratory mucosa of the nasal and paranasal cavities, the 2 major types of carcinoma are intestinal-type sinonasal adenocarcinoma (ITAC) and squamous cell carcinoma (SCCNC). ITAC is histopathologically similar to colorectal adenocarcinoma. However, it is unknown if this similarity extends to the pattern of genetic abnormalities involved. The aim of this study was to investigate if these results could be related to a possible role of MSI in these 2 types of nasal carcinoma.
Methods
DNA was extracted from frozen tumor samples of 34 ITAC and 25 SCCNC as well as corresponding blood samples of these patients. 5 mononucleotide microsatellite loci that show very little polymorfism between different individuals were amplified by multiplex PCR and analyzed by capillary electrophoresis.
Results
The allelic patterns showed normality for all 34 ITAC studied, whereas 2 SCCNC revealed an allelic shift for one of the 5 loci, indicating microsatellite instability.
Conclusions
MSI does not appear to play a role in ITAC as in colorectal adenocarcinoma. This finding is supported by immunohistochemistry studies of MMR protein expression levels. It remains to be elucidated what genetic mechanism propels tumorigenesis in diploid ITAC without gross chromosomal aberrations. In SSCNC, however, it cannot be excluded that MSI is involved in (a subset of) cases. Interestingly, only 1 of the 2 positive cases had the characterizing absence of chromosomal changes; the other carried multiple abnormalities.
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