title: Challenges and pitfalls in HNPCC screening by microsatellite analysis and immunohistochemistry.
abstract: Hereditary non-polyposis colorectal cancer (HNPCC) accounts for approximately 2 to 4% of the total colorectal cancer burden. For economic reasons a diagnostic "stepladder" is recommended. After evaluation of the family history, diagnostic microsatellite instability (MSI) analysis has found its place as a valuable screening tool for HNPCC. Immunohistochemical analysis can help to pinpoint the affected gene. The detection of a mutation in one of the responsible mismatch repair gene confirmed the diagnosis HNPCC. Here we demonstrate our experience of some important pitfalls that will be discussed in this study. In MSI testing, one potential source for false-negative results is intralesional heterogeneity. We demonstrate examples of a flat adenoma and a carcinoma, which required laser microdissection to correctly determine the microsatellite status. In these lesions manual microdissection, the most frequently applied method, was not sufficient. However, the number of cells obtained by using laser microdisssection can fall below a necessary minimum, which can also cause false-negative results of MSI analysis, as shown here in a mucinous carcinoma. In addition, evaluation of immunohistochemically stained tissue slides requires experience to avoid false-positive or false-negative interpretation. A case with two synchronous colorectal cancers revealed loss of MSH2 expression in one carcinoma, whereas the second carcinoma stained positively leading to a false-negative interpretation. In some cases, false-positive results can be obtained, if a perinuclear-staining pattern is interpreted as positive. In summary, there are several potential pitfalls in the molecular screening for HNPCC. Therefore the importance of correct interpretation of clinical data, immunohistochemistry, and microsatellite analysis in combination, performed by a pathologist with experience in molecular genetics is essential. In addition, laser microdissection of tumor areas that have been chosen by a pathologist is highly recommended in cases that cannot be resolved with manual microdissection.
authors.affiliation: Department of General Surgery, University of Göttingen, Germany.
authors.forename: Annegret
authors.initials: A
authors.lastname: Müller
authors.forename: Giuseppe
authors.initials: G
authors.lastname: Giuffre
authors.forename: Tina Bocker
authors.initials: TB
authors.lastname: Edmonston
authors.forename: Micaela
authors.initials: M
authors.lastname: Mathiak
authors.forename: Beate
authors.initials: B
authors.lastname: Roggendorf
authors.forename: Ernst
authors.initials: E
authors.lastname: Heinmöller
authors.forename: Thomas
authors.initials: T
authors.lastname: Brodegger
authors.forename: Giovanni
authors.initials: G
authors.lastname: Tuccari
authors.forename: Elisabeth
authors.initials: E
authors.lastname: Mangold
authors.forename: Reinhard
authors.initials: R
authors.lastname: Buettner
authors.forename: Josef
authors.initials: J
authors.lastname: Rüschoff
mesh_terms: D000236:Adenoma / Q000175:diagnosis / Q000235:genetics; D014408:Biomarkers, Tumor / Q000096:biosynthesis; D002277:Carcinoma / Q000175:diagnosis / Q000235:genetics; D002454:Cell Differentiation; D002467:Cell Nucleus / Q000378:metabolism; D015179:Colorectal Neoplasms / Q000175:diagnosis* / Q000235:genetics*; D003123:Colorectal Neoplasms, Hereditary Nonpolyposis / Q000175:diagnosis* / Q000235:genetics*; D004273:DNA, Neoplasm / Q000032:analysis; D004268:DNA-Binding Proteins / Q000378:metabolism; D005188:False Negative Reactions; D005260:Female; D006801:Humans; D007150:Immunohistochemistry; D007834:Lasers; D008297:Male; D008403:Mass Screening; D018895:Microsatellite Repeats; D008875:Middle Aged; D051718:MutS Homolog 2 Protein; D011518:Proto-Oncogene Proteins / Q000378:metabolism
chemical_list: D014408:Biomarkers, Tumor; D004273:DNA, Neoplasm; D004268:DNA-Binding Proteins; D011518:Proto-Oncogene Proteins; C497172:MSH2 protein, human; D051718:MutS Homolog 2 Protein