Value of staining intensity in the interpretation of immunohistochemistry for tumor markers in colorectal cancer

The purpose of this study was to determine whether staining intensity in conjunction with the percentage of positive tumor cells should be used as an indicator of protein expression detected by immunohistochemistry. A tissue microarray of 1,197 colorectal cancers was immunostained for p53, Her2/neu, epidermal growth factor receptor (EGFR), adenomatosis polyposis coli (APC), and β-catenin. Immunoreactivity was described by the percentage of positive tumor cells (percent positivity) and by the staining intensity (weak, moderate, strong). The interobserver reproducibility of both was evaluated by two pathologists. The association of T stage, N stage, tumor grade, vascular invasion, and survival with percent positivity, staining intensity, and the combination of both was assessed. In univariate analysis, protein expression assessed by percent positivity resulted in 11 significant associations between the proteins and clinico-pathological features. Eight of these 11 were also demonstrated using only the degree of staining intensity. However, more than half of the associations identified by percent positivity alone were lost when staining intensity was also analyzed in combination with the percentage of positive tumor cells. A scoring method based on percent positivity, rather than on staining intensity, for p53, Her2/neu, EGFR, APC, and β-catenin is reproducible and appears to be sufficient for establishing associations of the selected tumor markers with most clinico-pathological feature

SnoN expression is differently regulated in microsatellite unstable compared with microsatellite stable colorectal cancers

BACKGROUND: SnoN is an important regulator of the transforming growth factor beta (TGFβ) signalling pathway and has been shown to exhibit both tumour promotion and suppression activity. METHODS: To further explore the role of this complex molecule in colorectal tumorigenesis, we examined 52 paired normal and tumour colorectal specimens stratified by level of microsatellite instability; 18 with high-level microsatellite instability (MSI-H) and 34 microsatellite stable (MSS). SnoN transcript expression was quantitated by real-time PCR and analysed with respect to clinical indicators of prognosis. RESULTS: Within the MSI-H subgroup, SnoN was commonly either up-regulated (6/18, 33%) or down-regulated (7/18, 39%). A significantly different distribution of SnoN expression was observed in MSS cancers compared with MSI-H (P ≤ 0.001). Whilst 17/34 (50%) of MSS tumours demonstrated up-regulation, none showed down-regulated expression. Within the MSI-H subgroup, up-regulation was significantly correlated with lack of repeat tract mutation in the TGFβRII gene (P ≤ 0.025), suggesting that SnoN is more frequently up-regulated in the presence of functional TGFβ signalling. CONCLUSION: Together these data support the notion that SnoN has both oncogenic and tumour suppressive properties depending on other genetic changes within the tumour, and that the MSI-H pathway of colorectal tumorigenesis presents an excellent model for the study of these opposing functions

Linkage to chromosome 2q32.2-q33.3 in familial serrated neoplasia (Jass syndrome)

Causative genetic variants have to date been identified for only a small proportion of familial colorectal cancer (CRC). While conditions such as Familial Adenomatous Polyposis and Lynch syndrome have well defined genetic causes, the search for variants underlying the remainder of familial CRC is plagued by genetic heterogeneity. The recent identification of families with a heritable predisposition to malignancies arising through the serrated pathway (familial serrated neoplasia or Jass syndrome) provides an opportunity to study a subset of familial CRC in which heterogeneity may be greatly reduced. A genome-wide linkage screen was performed on a large family displaying a dominantly-inherited predisposition to serrated neoplasia genotyped using the Affymetrix GeneChip Human Mapping 10 K SNP Array. Parametric and nonparametric analyses were performed and resulting regions of interest, as well as previously reported CRC susceptibility loci at 3q22, 7q31 and 9q22, were followed up by finemapping in 10 serrated neoplasia families. Genome-wide linkage analysis revealed regions of interest at 2p25.2-p25.1, 2q24.3-q37.1 and 8p21.2-q12.1. Finemapping linkage and haplotype analyses identified 2q32.2-q33.3 as the region most likely to harbour linkage, with heterogeneity logarithm of the odds (HLOD) 2.09 and nonparametric linkage (NPL) score 2.36 (P = 0.004). Five primary candidate genes (CFLAR, CASP10, CASP8, FZD7 and BMPR2) were sequenced and no segregating variants identified. There was no evidence of linkage to previously reported loci on chromosomes 3, 7 and 9

Lower Cancer Incidence in Amsterdam-I Criteria Families Without Mismatch Repair Deficiency: Familial Colorectal Cancer Type X

Approximately 60% of families that meet the Amsterdam-I criteria (AC-I) for hereditary nonpolyposis colorectal cancer (HNPCC) have a hereditary abnormality in a DNA mismatch repair (MMR) gene. Cancer incidence in AC-I families with MMR gene mutations is reported to be very high, but cancer incidence for individuals in AC-I families with no evidence of an MMR defect is unknown

JR: Role of the pathologist in the diagnosis of hereditary nonpolyposis colorectal cancer

Abstract. The aim of this paper is to indicate how the pathologist may suspect a diagnosis of hereditary non-polyposis colorectal cancer (HNPCC) on the basis of histological criteria and patient age alone. A single morphological feature, namely the presence of intra-epithelial lymphocytes (tumor infiltrating lymphocytes), identifies the majority of colorectal cancers (CRC) with the DNA microsatellite instability-high phenotype. A number of pathological criteria can help to distinguish HNPCC from sporadic MSI-H CRC, though age below 60 years is an important pointer towards HNPCC. Immunohistochemistry to demonstrate loss of expression of DNA mismatch repair genes serves as a highly reliable test of mismatch repair deficiency if antibodies to hMLH1, hMSH2, hMSH6 and hPMS2 are employed

Pathology of hereditary nonpolyposis colorectal cancer

The magnitude of the pathologist's role in the diagnosis of hereditary nonpolyposis colorectal cancer (HNPCC) is underestimated. The diagnostic features are not specific to HNPCC cancers, but relate to all cancers showing high levels of DNA microsatellite instability (MSI-H). Three major groups of MSI-H cancers can be recognized by histopathological criteria: (1) right-sided poorly differentiated cancers, (2) right-sided mucinous cancers, and (3) adenocarcinomas in any location showing tumor-infiltrating (intraepithelial) lymphocytes (TIL). The poorly differentiated cancers are relatively well circumscribed and the cells are arranged in sheets or trabeculae. TIL may be very numerous in poorly differentiated cancers. The presence of TIL as estimated in HandE sections equates with a percentage of intraepithelial T cells (CD3) in the range of 4 to 30%. Most of the T cells are CD8 (cytotoxic T cells). Peritumoral lymphocytes and the so-called Crohn's-like reaction are associated with TIL, but are harder to quantify. Of the 15% of colorectal cancers that are MSI-H, 13% will be sporadic and 2% will occur in the context of HNPCC. HNPCC should be suspected if the patient is young (less than 55 years) because sporadic MSI-H cancers (associated with hypermethylation of the promoter region of hMLH1) occur almost exclusively in elderly subjects. Workup of a suspected case should include DNA microsatellite testing with a panel of mononucleotide (e.g,, BAT26, BAT25) and dinucleotide (e.g., D5S346, D2S123, and D177S250) markers before referral to a cancer family or clinical genetics clinic. Immunohistochemical staining for hMLH1 and hMSH2 identifies the underlying mutation in a proportion of cases. The colorectal adenoma is the usual precursor lesion in HNPCC, though serrated polyps are implicated in a small subset