Identification of patients with (atypical) MUTYH-associated polyposis by KRAS2 c.34G > T prescreening followed by MUTYH hotspot analysis in formalin-fixed paraffin-embedded tissue.
OBJECTIVE
To assess the feasibility of identifying patients with (atypical) MUTYH-associated polyposis (MAP) by KRAS2 c.34G > T prescreening followed by MUTYH hotspot mutation analysis in formalin-fixed paraffin-embedded tissue (FFPE).


METHODS
We collected 210 colorectal FFPE tumors from 192 individuals who presented with <10 adenomas or familial mismatch repair proficient colorectal carcinomas with <10 concomitant adenomas. The tissues were tested for somatic KRAS2 mutations and for three Dutch hotspot MUTYH germ line mutations (p.Tyr165Cys, p.Gly382Asp, and p.Pro391Leu) by sequencing analysis.


RESULTS
The c.34G > T, KRAS2 transversion was detected in 10 of 210 tumors. In one of these 10 cases, a monoallelic p.Gly382Asp MUTYH mutation was found and a full MUTYH analysis in leukocyte DNA revealed an unclassified variant p.Met269Val. This was in a 61-year-old patient with a cecum carcinoma and three adenomas. After further requests, her family case history revealed that her brother had had between 10 and 15 adenomas and turned out to carry both MUTYH germ line mutations. MUTYH hotspot mutation screening in 182 patients without the somatic c.34G > T KRAS2 mutation led to the detection of three monoallelic germ line MUTYH mutation carriers.


CONCLUSIONS
KRAS2 c.34G > T somatic prescreening, followed by MUTYH hotspot mutation analysis when positive, can identify patients with (atypical) MAP. If heterozygous hotspot MUTYH mutations are identified, a complete germ line MUTYH mutation screening should be carried out if possible. Immediate MUTYH hotspot mutation analysis is a practical alternative in patients with >10 adenomas or in cases of multiple colorectal carcinomas in one generation for which only FFPE tissue is available.
van Puijenbroek
Marjo
M
Department of Pathology, Leiden University Medical Center, Leiden, the Netherlands.
Nielsen
Maartje
M
Tops
Carli M J
CM
Halfwerk
Hans
H
Vasen
Hans F A
HF
Weiss
Marjan M
MM
van Wezel
Tom
T
Hes
Frederik J
FJ
Morreau
Hans
H
D011125:Adenomatous Polyposis Coli / Q000235:genetics*; D000328:Adult; D000368:Aged; D045647:DNA Glycosylases / Q000235:genetics*; D053843:DNA Mismatch Repair; D004252:DNA Mutational Analysis; D005260:Female; D005557:Formaldehyde; D005820:Genetic Testing; D018095:Germ-Line Mutation / Q000235:genetics; D006801:Humans; D008297:Male; D053842:Microsatellite Instability; D008875:Middle Aged; D016612:Paraffin Embedding; D010375:Pedigree; D016133:Polymerase Chain Reaction; D011518:Proto-Oncogene Proteins / Q000235:genetics*; D016283:Proto-Oncogene Proteins p21(ras); D016707:Tissue Fixation; D018631:ras Proteins / Q000235:genetics*
C117307:KRAS protein, human; D011518:Proto-Oncogene Proteins; D005557:Formaldehyde; D045647:DNA Glycosylases; C061738:mutY adenine glycosylase; D016283:Proto-Oncogene Proteins p21(ras); D018631:ras Proteins