Allelic loss is heterogeneous throughout the tumor in colorectal carcinoma

Prognostic role of methylated free circulating DNA in colorectal cancer

DNA hypermethylation is frequently found in colorectal cancer (CRC). Methylation of helicase-like transcription factor (HLTF) and hyperplastic polyposis 1 (HPP1) are potential and carcinoembryonic antigen (CEA) is an established prognostic factor in serum of patients with CRC. The aim of this study was to perform a direct comparison of the prognostic roles of these markers. Methylation status of HLTF and HPP1 was examined in pretherapeutic sera of 311 patients with CRC and matched primary tissues of 54 stage IV patients using methylation-specific quantitative PCR. CEA was determined using an immunoenzymometric assay. Methylation of HLTF and HPP1 DNA in serum significantly correlated with tumor size, stage, grade and metastatic disease. HPP1 methylation correlated with nodal status. Overall survival was shortened in case of methylation of HLTF or HPP1 or elevated levels of CEA (p < 0.0001 for all). In stage IV, patients survival was impaired if HLTF (p = 0.0005) or HPP1 (p = 0.0003) were methylated or CEA was above the median of 27 ng/ml (p = 0.002). Multivariate analysis revealed that methylation of HLTF [hazard ratio (HR) 1.8, p = 0.0438], HPP1 (HR 1.6, p = 0.0495) and CEA >27 ng/ml (HR 1.7, p = 0.0317) were independent prognostic factors in stage IV. The combination of any two or all three of these factors outperformed each marker on its own. In conclusion, the presence of methylated DNA of the genes HLTF or HPP1 in serum are independent prognostic factors in metastasized CRC. Prospective validation is required to determine their usefulness in clinical routine along with the established marker CEA.

Detection of DNA hypermethylation in remote media of patients with colorectal cancer: new biomarkers for colorectal carcinoma

Colorectal cancer is the third most common cancer and a major cause of cancer-related mortality. The lifetime risk to develop colorectal cancer is 6% in the Western world, and one third of the affected people will ultimately die from this disease. Colorectal carcinomas develop slowly over a period of several years. Therefore, identifying people with precancerous lesions holds the potential to reduce the incidence and mortality of colorectal cancer. Apart from mutations and chromosomal imbalances, inactivation of tumor suppressor genes by DNA hypermethylation has been recognized as an important mechanism driving colorectal carcinogenesis. In recent years, screening tests have been developed that rely on the detection of DNA hypermethylation in remote media to identify people suffering from asymptomatic colorectal cancers at early stages. Apart from their diagnostic value, methylation markers hold the potential to be used as prognostic markers. Here, we summarize the recent development of DNA methylation markers for colorectal cancer in remote media with regard to their diagnostic and prognostic value.

Microsatellite instability and loss of heterozygosity at chromosomal location 18q: prospective evaluation of biomarkers for stages II and III colon cancer--a study of CALGB 9581 and 89803

PURPOSE

Colorectal cancer (CRC) develops as a result of a series of accumulated genomic changes that produce oncogene activation and tumor suppressor gene loss. These characteristics may classify CRC into subsets of distinct clinical behaviors.

PATIENTS AND METHODS

We studied two of these genomic defects-mismatch repair deficiency (MMR-D) and loss of heterozygosity at chromosomal location 18q (18qLOH)-in patients enrolled onto two phase III cooperative group trials for treatment of potentially curable colon cancer. These trials included prospective secondary analyses to determine the relationship between these markers and treatment outcome. A total of 1,852 patients were tested for MMR status and 955 (excluding patients with MMR-D tumors) for 18qLOH.

RESULTS

Compared with stage III, more stage II tumors were MMR-D (21.3% v 14.4%; P < .001) and were intact at 18q (24.2% v 15.1%; P = .001). For the combined cohort, patients with MMR-D tumors had better 5-year disease-free survival (DFS; 0.76 v 0.67; P < .001) and overall survival (OS; 0.81 v 0.78; P = .029) than those with MMR intact (MMR-I) tumors. Among patients with MMR-I tumors, the status of 18q did not affect outcome, with 5-year values for patients with 18q intact versus 18qLOH tumors of 0.74 versus 0.65 (P = .18) for DFS and 0.81 versus 0.77 (P = .18) for OS.

CONCLUSION

We conclude that MMR-D tumor status, but not the presence of 18qLOH, has prognostic value for stages II and III colon cancer.

Methylation of NEUROG1 in serum is a sensitive marker for the detection of early colorectal cancer

OBJECTIVES

Colorectal cancer is the third most common cancer and a major cause of cancer-related deaths. Early detection of colonic lesions can reduce the incidence and mortality of colorectal cancer. Colonoscopy is the screening test for colorectal cancer with the highest efficacy, but its acceptance in the general public is rather low. To identify suitable tumor-derived markers that could detect colorectal cancer in blood samples, we analyzed the methylation status of a panel of genes in sera of affected patients.

METHODS

Using methylation-specific quantitative PCR, we analyzed the methylation of ten marker genes in sera of healthy individuals and patients with colorectal cancer.

RESULTS

Only HLTF, HPP1/TPEF, and NEUROG1 DNA methylation was detectable in at least 50% of patients with colorectal cancers. Whereas HLTF and HPP1/TPEF preferentially detected advanced and metastasized colorectal cancers, NEUROG1 methylation was detectable in UICC stages I-IV at a similar rate. Compared with other methylation markers, such as ALX4, SEPT9, and vimentin, NEUROG1 shows a higher sensitivity for colorectal cancer at UICC stages I and II. At a specificity of 91%, NEUROG1 reached a sensitivity of 61% (confidence interval, 50.4-70.6%) for the detection of colorectal cancers. Furthermore, detection of NEUROG1 methylation was independent of age and gender.

CONCLUSIONS

Methylation of the NEUROG1 gene is frequently found in sera of patients with colorectal cancers independent of tumor stage. The quantitative detection of NEUROG1 DNA methylation in serum is a suitable approach for the non-invasive screening for asymptomatic colorectal cancer.

Circulating nucleic acids (CNAs) and cancer--a survey

It has been known for decades that it is possible to detect small amounts of extracellular nucleic acids in plasma and serum of healthy and diseased human beings. The unequivocal proof that part of these circulating nucleic acids (CNAs) is of tumor origin, initiated a surge of studies which confirmed and extended the original observations. In the past few years many experiments showed that tumor-associated alterations can be detected at the DNA and RNA level. At the DNA level the detection of point mutations, microsatellite alterations, chromosomal alterations, i.e. inversion and deletion, and hypermethylation of promoter sequences were demonstrated. At the RNA level the overexpression of tumor-associated genes was shown. These observations laid the foundation for the development of assays for an early detection of cancer as well as for other clinical means.

Clonality of pituitary tumours: more complicated than initially envisaged?

The application of allelotype microsatellite polymorphisms and X chromosome inactivation analysis in samples from women allow assessment of clonality. Early studies showed that sporadic human pituitary tumors are benign adenomas of monoclonal origin. This implies that they arise from de novo somatic mutation(s) within a single pituitary cell. However, the evidence obtained from a number of studies indicate that morphology cannot predict clonality, clonality within a given tumour may be multiple or single, multiple tumours arising on the background of hyperplasia may be of identical or differing clonality, and multiple "sporadic" tumours within a gland may be of differing clonal origin. Thus, while the early available evidence indicated that pituitary tumours appear largely monoclonal, it is simplistic to assume that this is inevitable and that these cannot be multiclonal in origin. These observations would be entirely compatible with an initiating stimulus resulting in hyperplasia of specific cell types in the pituitary, which itself gives rise to several distinct clones with variable potential to develop into tumours. Such stimuli might include hypothalamic trophic factors, intrapituitary growth factors, or pituitary specific oncogenes.

A systematic review and meta-analysis of the relationship between chromosome 18q genotype, DCC status and colorectal cancer prognosis

Results from studies investigating the relationship between colorectal cancer survival and chromosome 18q allelic imbalance (AI)/loss of DCC expression (LOE) have been inconsistent. We have reviewed and pooled published studies to estimate the prognostic significance of chromosome 18q status more precisely. Data from 27 studies were eligible. Survival data were pooled using standard meta-analysis techniques. Considerable variation between assessment method, marker choice, and threshold for assigning AI/LOE was observed. Pooling data from a 2189 cases from 17 studies showed significantly worse overall survival in patients with AI/LOE (HR = 2.00, 95%CI: 1.49-2.69), maintained both in the adjuvant setting (HR = 1.69, 95%CI:1.13-2.54), and also by method (HR = 1.67, 95%CI: 1.19-2.36, genotyping microsatellites; HR = 3.00, 95%CI: 1.98-4.56, immunohistochemistry). There was however evidence of heterogeneity and publication bias. Cancers with chromosome 18q loss appear to have a poorer prognosis. Prospective studies using consistent methodology are needed to precisely quantify its effect and role in patients with stage II-III disease.

Prognostic and Predictive Relevance of DNAM-1, SOCS6 and CADH-7 Genes on Chromosome 18q in Colorectal Cancer

PURPOSE

Chromosome 18q deletion has been described as a negative prognostic factor in colorectal cancer (CRC). The relationship between its supposed negative prognostic influence and the inactivation of candidate tumor suppressors deleted in colorectal cancer, Smad2 and Smad4 has not been definitively established. The aim of the present study was to evaluate the genetic status of three novel putative tumor suppressors, Cadh-7, DNAX accessory molecule-1 (Dnam-1) and suppressor of cytokine signaling (Socs6) on chromosome 18q and to correlate molecular results with patient survival and benefit from adjuvant chemotherapy.

EXPERIMENTAL DESIGN

One hundred and ninety representative patient samples from a randomized multicenter study of the Swiss Group for Clinical Cancer Research of 5-fluorouracil (5-FU)- based adjuvant chemotherapy were screened for the gene copy status of Cadh-7, Socs6 and Dnam-1 using real-time quantitative PCR assay, and the molecular results were correlated with clinical outcome.

RESULTS

Loss of gene copy number was found in 26.8, 37.9 and 54.2% for Cadh-7, Dnam-1 and Socs6, respectively. Only Dnam-1 deletion was an independent negative prognostic factor for the 5-year overall survival (OS) in the untreated group of patients (hazard ratio = 2.44; p = 0.01). On the contrary, loss of Cadh-7 gene copy number was a favourable prognostic factor for disease-free survival (hazard ratio = 0.43; p = 0.03) and OS (hazard ratio = 0.29; p = 0.01) in the untreated control population. Furthermore and most importantly, patients with Dnam-1 deletion who received adjuvant chemotherapy had a significantly lower risk of death compared to untreated patients with Dnam-1 deletion (hazard ratio = 0.51; p = 0.05), whereas those with Dnam-1 retention did not derive any benefit from 5-FU-based treatment (hazard ratio = 1.68; p = 0.16).

CONCLUSIONS

Loss of Dnam-1 gene copy number and retention of Cadh-7 might be indicators of worse prognosis, and Dnam-1 deletion might predict for a beneficial response to adjuvant 5-FU-based chemotherapy in patients with CRC. The confirmation of our findings in large independent randomized studies is needed.

Fluorescence in situ hybridisation analysis of chromosomal aberrations in gastric tissue: the potential involvement of Helicobacter pylori

In this series of experiments, a novel protocol was developed whereby gastric cells were collected using endoscopic cytology brush techniques, and prepared, such that interphase fluorescence in situ hybridization (FISH) could be performed. In total, 80 distinct histological samples from 37 patients were studied using four chromosome probes (over 32,000 cells analysed). Studies have previously identified abnormalities of these four chromosomes in upper GI tumours. Using premalignant tissues, we aimed to determine how early in Correa's pathway to gastric cancer these chromosome abnormalities occurred. Aneuploidy of chromosomes 4, 8, 20 and 17(p53) was detected in histologically normal gastric mucosa, as well as in gastritis, intestinal metaplasia, dysplasia and cancer samples. The levels of aneuploidy increased as disease severity increased. Amplification of chromosome 4 and chromosome 20, and deletion of chromosome 17(p53) were the more common findings. Hence, a role for these abnormalities may exist in the initiation of, and the progression to, gastric cancer. Helicobacter pylori infection was determined in premalignant tissue using histological analysis and PCR technology. Detection rates were comparable. PCR was used to subtype H. pylori for CagA status. The amplification of chromosome 4 in gastric tissue was significantly more prevalent in H. pylori-positive patients (n=7) compared to H. pylori-negative patients (n=11), possibly reflecting a role for chromosome 4 amplification in H. pylori-induced gastric cancer. The more virulent CagA strain of H. pylori was associated with increased disease pathology and chromosomal abnormalities, although numbers were small (CagA+ n=3, CagA- n=4). Finally, in vitro work demonstrated that the aneuploidy induced in a human cell line after exposure to the reactive oxygen species (ROS) hydrogen peroxide was similar to that already shown in the gastric cancer pathway, and may further strengthen the hypothesis that H. pylori causes gastric cancer progression via an ROS-mediated mechanism.

p53 codon 72 polymorphism and susceptibility malignancy of colorectal cancer in Taiwan

PURPOSE

The p53 tumor suppressor gene plays two important roles in genomic stability: blocking cell proliferation after DNA damage until it has been repaired, and starting apoptosis if the damage is too critical. A recent report suggests that a polymorphism of the p53 tumor suppressor gene that results in the substitution of a proline residue with an arginine residue at position 72 of the p53 protein might act as a risk factor in the malignant transformation of colorectal adenoma to cancer.

METHODS

In our study, the samples consisted of 150 patients were analyzed for the mutation in the p53 gene. The age of 150 patients (46 women and 104 men) ranged from 30 to 91 years (mean age 68.46 years).

RESULTS

The polymorphism showed 52.04% mutant in the codon 72 of exon 4 in the Taiwanese population. Both of the chi-square for trend test (chi-square = 4.97, p = 0.034) and logistic regression (p = 0.037, odds ratio = 1.699) showed significant differences in the distribution of polymorphism of codon 72 in the p53 gene and Dukes classification of colorectal cancer.

CONCLUSIONS

There were significant relationship between the polymorphism of codon 72 and the malignancy of colorectal cancer in Taiwanese population. There is 1.70 times in each grade change (Dukes A-D) more risk of CCC polymorphism than that of CCG polymorphism of codon 72 of exon 4.

Clinical significance of allelotype profiling for urothelial carcinoma

OBJECTIVES

To perform a global loss of heterozygosity (LOH) analysis on a cohort of urothelial carcinoma to investigate the clinical implication of specific chromosomal loss. Allelic deletions detected as LOH have been used to study the markers for carcinogenesis.

METHODS

We examined the allelic loss on 14 chromosomal regions in a total of 71 cases of urothelial carcinoma. The results were analyzed in relation to biologic indicators of urothelial carcinoma and the clinical outcome with a mean follow-up of 101 months.

RESULTS

The incidence of LOH in order of frequency was 9p (54.9%), 9q (49.3%), 13q (40.8%), 14q (40.8%), 10q (39.4%), 17p (39.4%), 8p (38.0%), 21q (36.6%), 11p (31.0%), 18q (23.9%), 4q (21.1%), 3p (16.9%), 6q (14.1%), and 1q (8.5%). Positive association with one of the indicators was observed in 3p, 9p, 9q, 10q, 14q, and 18q. The chromosomes that correlated with two biologic indicators were 4q, 6q, 11p, 17p, and 21q. Univariate analysis found that patients having combined 9p and 14q deleted tumors had particularly poor long-term survival compared with those with other patterns of chromosomal alterations (P = 0.01). In the multivariate model, nonpapillary tumors had a greater risk of recurrence, and stage classification was the only important indicator in predicting patient survival (P = 0.04).

CONCLUSIONS

LOH assessment does not provide independent prognostic value compared with stage classification. However, chromosomes 4q, 6q, 9p, 11p, 14q, 17p, and 21q may harbor important tumor suppressor genes involved in the progression of urothelial carcinogenesis.

Distribution of genetic variants in preneoplastic areas of colorectal tumours

AIMS

Loss of heterozygosity (LOH) may vary almost randomly within a colorectal tumour due to the heterogeneous morphologic character of these tumours. Despite this, as a rule, single biopsies are the source of genetic material used in studies of markers important for prognosis, clinical behaviour of the disease, or susceptibility of specific tumours to different treatment modalities.

METHODS

To evaluate the importance of intratumoural variation for the results of analysis of LOH and point mutations in colorectal cancer and to determine the frequency of genetic alterations in different types of pre-neoplastic areas of the tumours, 36 consecutively operated patients with colorectal cancer were studied. After fixation, specimens were mounted on large slides containing the whole tumour. The specimens were sub classified into different areas defined as normal tissue, normal tissue closely adjacent the tumour mass, adenoma, dysplasia and invasive cancer cells. These areas were dissected and subjected to DNA extraction.

RESULTS

The extracted genomic DNA was studied for LOH at chromosome 5q, 17p, and 18q and for k-ras mutations. Overall, a correlation between the intratumoural degree of neoplastic progression and the frequency of LOH and k-ras mutations was seen. These correlations were significant (p<0.008) except for dysplasia/adenomatous tissue versus invasive cancer. Microsatellite instability was found in 9% of the tumours, all except one in invasive parts of the tumours.

CONCLUSIONS

This study demonstrates a statistical correlation between intratumoural differences in neoplastic degree of dedifferentiation and genetic instability in terms of LOH and point mutations of the k-ras gene in colorectal carcinoma. The importance of a careful dissection in order to localise the region with the highest probability of genetic aberrations and multiple biopsing must not be neglected. The observation that the prevalence of k-ras mutations and LOH are correlated to the degree of dedifferentiation within a colorectal tumour is in line with the concept that selected cell clones are responsible for the neoplastic progression of the tumour.

SMAD7 is a prognostic marker in patients with colorectal cancer

Chromosomal region 18q21 is frequently deleted in colorectal cancer (CRC) and is associated with poor prognosis. Potential tumor suppressor mechanisms altered by 18q21 deletion include mediation of TGFbeta signaling by SMADs. Following the definition of SMAD4 deletion as a negative predictive marker for chemotherapy benefit in patients with CRC, we aimed to evaluate the clinical relevance of the deletion of other SMAD genes clustered in this region: SMAD2 and SMAD7 in 264 CRC biopsies from a previous clinical study. In contrast to SMAD2 deletion, for which no clinical relevance was observed, hazard ratios (HR) in a multivariate analysis associated with SMAD7 deletion [overall survival (OS): HR = 0.43, p = 0.0012; disease-free survival (DFS): HR = 0.50, p = 0.0033] indicated a favorable outcome for these patients. In addition, SMAD7 duplication had a hazardous effect on survival [OS: HR = 2.10, p = 0.020; DFS: HR = 2.06, p = 0.015]. Moreover, the HRs associated with one additional copy of SMAD7 were 1.76, p = 0.00024 [OS] and 1.64, p = 0.00048 [DFS] respectively, showing a graded effect of SMAD7 on patient outcome depending on gene copy number that suggests a dose-and-effect basis. Since SMAD7 blocks TGFbeta signaling, these data are consistent with the loss of SMAD7 rendering carcinoma cells more sensitive to cell growth arrest/apoptotic effect of TGFbeta, whereas gain of SMAD7 function might result in TGFbeta resistance, thereby emphasizing the role of TGFbeta in tumor suppression.

Mutations in the p53 tumor suppressor gene in colorectal cancer in Taiwan

Mutations in the tumor suppressor gene p53 have been reported as occurring prevalently in a wide range of human tumors. Detection of a mutated p53 is thought to provide useful information for the clinical management of colorectal neoplasm. In this study, we used polymerase chain reaction/single-strand conformation polymorphism (PCR/SSCP) and sequencing analysis to rapidly screen for mutations in p53 in colorectal cancer in Taiwan. Genomic DNA was purified from colorectal cancer specimens obtained from 80 patients at a teaching hospital in southern Taiwan. Primer sets were designed to amplify fragments within exons 4-8 of p53. We found p53 mutations in 38 of 80 patients. This is the first identification of a mutation at codon 143 of p53 in colorectal cancer in Taiwan. In addition, we found two insertions in exon 5 of p53. The p53 mutation rate among colorectal tumors in Taiwan, found in this study, is 43%. The results indicate that p53 mutation is not significantly associated with tumor grade, age, or gender (p > 0.05). We found that two-fifths of colorectal cancer patients in Taiwan have a p53 mutation, which could be used as a marker of colorectal cancer.

Counting alleles to predict recurrence of early-stage colorectal cancers

BACKGROUND

Chromosome imbalances occur in many cancers and represent important biological properties of tumours. However, measurements of such imbalances are difficult. We used a new, quantitative approach to investigate the prognostic value of chromosome imbalances in early-stage colorectal cancers.

METHODS

We studied 180 patients with no evidence of lymph-node or distant metastases at the time of surgery. DNA from paraffin-embedded tumours was tested for imbalances of chromosome 8p and 18q by digital SNP (single-nucleotide polymorphism)-a technique in which each allele in a sample is directly counted. Surviving patients had median follow-up of 68 months, and disease recurrence was used as the clinical endpoint.

FINDINGS

Tumours were divided into three groups: "L" tumours (n=93) had allelic imbalances of chromosomes 8p and 18q, "L/R" tumours (n=60) had allelic imbalances of either chromosome 8p or 18q but not both, and "R" tumours (n=27) retained allelic balance for both chromosomes. 5-year disease-free survival was 100% (95% CI 80-100) for patients with R tumours, 74% (61-87) for patients with L/R tumours, and 58% (47-69) for those with L tumours. These differences were significant (p<0.0001) and were independent of other variables--eg, Duke's stage A tumours of class L were much more likely to recur than Duke's stage B tumours of class R (p=0.002).

INTERPRETATION

In patients without metastasis, allelic imbalance is a better predictor of prognosis than histopathological stage.

Restriction enzymes in the analysis of genetic alterations responsible for cancer progression

BACKGROUND

Molecular approaches are increasingly being employed to dissect the genetic changes accompanying tumour formation. These methods can often be confusing to the non-specialist as they include complex molecular steps. This can reduce the usefulness of such molecular data to clinicians. The authors aim to aid interpretation of molecular studies in general by presenting a comprehensive review of one molecular approach, i.e. the use of restriction enzymes in molecular studies of tumour development.

METHOD

A review was made of the molecular studies that have employed restriction enzymes in gastrointestinal cancer research. These studies have used restriction enzymes to analyse point mutation induction, gene methylation status and the deletion of chromosomal loci. In addition, emphasis is placed on some of the important considerations for the molecular analysis of tumours that can affect the molecular data obtained.

RESULTS

Restriction enzyme digestion has played, and continues to play, a major role in analysing the genetic changes in cancer. Many adaptations of basic restriction enzyme methodologies have enhanced the application of this approach in cancer genetics.

CONCLUSION

The availability of 200 different restriction enzymes, each recognizing different sequences in DNA, has been invaluable in studying cancer genetics. It is hoped that current advances in protein engineering will facilitate the creation of novel restriction enzymes with tailor-made sequence specificities. This will further improve the applicability of restriction enzymes in cancer genetics.

WNT1 inducible signaling pathway protein 3, WISP-3, a novel target gene in colorectal carcinomas with microsatellite instability

BACKGROUND & AIMS

Microsatellite instability (MSI) is the phenotype of colorectal carcinomas with defect mismatch repair. Genes with repetitive sequences within their coding regions are targets for mutations in these tumors. We have evaluated 2 novel candidate genes for potential involvement in development of MSI colorectal carcinomas and compared them with alterations in known target genes.

METHODS

The MSI status was determined by multiplex polymerase chain reactions (PCRs) of 5-17 markers in a Norwegian series of 275 colorectal carcinomas. All MSI tumors were analyzed for gene mutations using fluorescence PCR followed by capillary electrophoresis. Two novel candidate genes, WNT1-inducible signaling pathway protein 3 (WISP-3) and caspase-1, and 9 known target genes were analyzed.

RESULTS

Thirteen percent of the tumors were MSI-high (H) and 12% were MSI-low (L). Thirty-three of 37 MSI-H vs. 1 of 34 MSI-L tumors showed mutations in the target genes (P < 0.001). WISP-3 was mutated in 31% of the MSI-H tumors. The frequencies of frameshift mutations in the known target genes were comparable with other studies.

CONCLUSIONS

The relative high frequency of mutation, higher than those seen for other known target genes, the predicted truncation of the protein product, and the homology with WISP-1 and WISP-2, 2 proteins induced downstream of WNT1 signaling, strongly suggest WISP-3 as a novel target in development of MSI-H colorectal carcinomas.

Monoclonality of endocrine tumours: What does it mean?

It is believed and hoped that clonality assignment of tumours predicts long-term behaviour, narrows the search for the putative pathogenic event or events, identifies the extent of involvement of surrounding and distant tissues and assesses the completeness of surgical clearance. It should define optimal therapeutic strategies, such as gene therapy, and the most fruitful directions for research. Because the histological characteristics that are central to establishing prognosis in most neoplasms are of limited value in endocrine tumours, the benefits of interpretation of clonality are potentially even more valuable and far-reaching in these tissues. So, can clonality be accurately defined and, if it can, can the distinction between a polyclonal expansion of cells that are simply 'obeying orders' and the presumed progeny of a single anarchic mutant be usefully made? This review comes to the conclusion that the answer is 'probably not'.