A tool to predict survival in stage IV entero-pancreatic NEN.

PURPOSE: Well-differentiated stage IV neuroendocrine neoplasms (NEN) have an extremely heterogeneous, unpredictable clinical behavior. Survival prognostic markers, such as the recently proposed NEP-Score, would be very useful for better defining therapeutic strategies. We aim to verify NEP-Score applicability in an independent cohort of stage IV well-differentiated (WD) gastroentero-pancreatic (GEP) NEN, and identify a derivate prognostic marker taking into account clinical and pathological characteristics at diagnosis. METHODS: Age, site of primary tumor, primary tumor surgery, symptoms, Ki67, timing of metastases of 27 patients (10 females; mean age at diagnosis 60.2 ± 2.9 years) with stage IV WD GEP NEN were evaluated to calculate the NEP-Score at the end of follow-up (NEP-T). We calculated the NEP-Score at diagnosis (NEP-D), which does not consider the appearance of new metastases during follow-up. Patients were subdivided according to whether they were alive or not at the end of follow-up (EOF) and an NEP-Score threshold was investigated to predict survival. RESULTS: Mean NEP-T and mean NEP-D were significantly lower in 15 live patients as compared to 12 deceased patients (p < 0.01) at EOF. We identified an NEP-D = 116 as the cutoff that significantly predicts survival. No gender differences were identified. CONCLUSIONS: In our series, we confirmed NEP-Score applicability. In addition, we propose NEP-D as a simple, quick and cheap prognostic score that can help clinicians in decision making. NEP-D threshold can predict NEN aggressiveness and may be used to define the best personalized therapeutic strategy.

Medullary-type poorly differentiated adenocarcinoma of the large bowel: a distinct clinicopathologic entity characterized by microsatellite instability and improved survival.

PURPOSE: Recent studies suggest the existence of a distinct class of poorly differentiated large bowel adenocarcinomas, usually termed medullary-type adenocarcinomas (MTAs). The aim of the present study was to accurately define the clinical, histopathologic, biologic, and genetic features of this tumor type. MATERIALS AND METHODS: Among 1,265 surgically resected sporadic colorectal carcinomas, 45 MTAs were identified on the basis of the following criteria: predominantly solid growth pattern (at least 70% of the tumor area) and lack of marked nuclear pleomorphism. The clinicopathologic, biologic, and genetic characteristics of MTAs were compared with those of a series of 457 common glandular colorectal adenocarcinomas. RESULTS: The significantly different clinicopathologic features of MTAs were proximal location, large size, invasion into adjacent organs, expanding pattern of growth, low incidence of distant metastases, more frequent conspicuous peritumoral lymphocytic infiltration, and Crohn's-like lymphoid reaction. Furthermore, young patients with MTAs often demonstrated a family history highly suggestive of a hereditary background. Unlike glandular adenocarcinomas, the large majority of MTAs were DNA diploid by flow cytometric analysis (21 of 25, 84%) and p53 negative by immunohistochemistry (36 of 41, 87.8%). In addition, 18 of the 20 MTAs examined by DNA microsatellite analysis demonstrated widespread microsatellite instability (90% of cases). Patients with MTAs showed a better clinical outcome with respect to patients with common poorly differentiated adenocarcinomas (PDAs) (P <.0001) and well- or moderately differentiated adenocarcinomas (WMDAs) (P =.133). In particular, none of the 33 patients with completely resectable stage II and III MTAs developed tumor recurrence during the observation period. Conversely, 24.7% of patients with stage II and III WMDAs and 48.9% of patients with stage II and III PDAs, who had undergone curative surgical resection, died of recurrent disease (P =.01 and P <.0001, respectively). CONCLUSION: All these data strongly indicate that MTAs represent a distinct pathologic entity, with specific histologic appearance and peculiar clinical and genetic features. These tumors need to be classified separately from other poorly differentiated colorectal carcinomas.

p53 expression in colorectal cancer: relation to tumor type, DNA ploidy pattern and short-term survival.

p53 protein expression was evaluated in a series of 204 primary colorectal adenocarcinomas by immunohistochemistry using frozen tissue sections and monoclonal antibody DO-7. Nuclear staining of more than 5% of neoplastic cells was observed in 124 (60.8%) adenocarcinomas, which were classified as p53 positive. p53 immunoreactivity was found to he unrelated to several clinical and pathologic variables, including age and sex of patient, tumor site, tumor stage, grade of differentiation, pattern of growth, degree of peritumoral lymphocytic infiltration, and venous invasion. A strong association was demonstrated between p53 immunostaining and tumor type. Only 4 of 21 mucinous carcinomas examined (19%) were p53 positive. Conversely, 120 of 183 (65.6%) nonmucinous adenocarcinomas showed positive p53 immunostaining (P <.0001). p53 expression also was related to the flow cytometric DNA ploidy pattern, aneuploid carcinomas with DI >1.20 showing higher frequency of p53 overexpression than DNA diploid, and aneuploid tumors with DI < or = 1.20 (P = .0003). No relationship was found between p53 expression and the Ki-67 proliferation index. With respect to the total study population (mean follow-up 33.4 months; range 19-47 months) the duration of overall survival was independent of p53 expression. In the group of 141 patients with stage I, stage II, and stage III disease who had undergone curative resection, positive p53 immunostaining was associated with poorer overall survival (P = .029). Subgroup analysis showed that the reduced survival conferred by p53 overexpression was confined to patients with stage III tumors (P = .027). However, in multivariate analysis, p53 expression failed to demonstrate independent prognostic significance. Our results indicate that immunohistochemical analysis of p53 expression provides valuable information for the understanding of colorectal cancer biology and clinical behavior.

Lymphoepithelial cyst of the pancreas.

A rare case of lymphoepithelial cyst of the pancreas is reported. Microscopically the cyst content consisted of keratinous material and the walls were lined by mature squamous epithelium surrounded by dense lymphoid tissue. Immunohistochemistry showed diffuse reactivity for CD20 and CD3 in the lymphoid tissue and uniform positivity for cytokeratins in the squamous epithelium. Although the histogenesis of lymphoepithelial cysts of the pancreas is not understood, awareness of this lesion is helpful in differentiating it from other pancreatic cystic lesions.

Cerebellar hemorrhage in xanthomatous neoplastiform lesion of vermis cerebelli. Case report.

A xanthomatous lesion of vermis cerebelli was removed successfully from the posterior fossa of a 19 years old girl with insulin-dependent diabetes and hypercholesterolemia, admitted for cerebellar hemorrhage. A review of literature shows that this is the first case of xanthomatous lesion presented with cerebellar hemorrhage. The pathogenesis of this lesion is reviewed as it relates to the presentation of this case.

Mucinous adenocarcinoma in chronic anorectal fistula.

Adenocarcinoma in association with chronic anal fistula is a rare disease which gives rise to difficult problems of diagnosis and treatment. A case of mucinous adenocarcinoma arising on a long standing fistula in ano is described. A patient with a long history of mucinous discharge, pain and perianal induration underwent a biopsy of the external opening of the fistula that showed mucinous infiltrating adenocarcinoma. After a colonoscopy and a preoperative abdominal CT scan, she underwent a successful abdominoperineal resection with adjuvant chemoradiation therapy. Diagnosis of this condition is often difficult; deep and multiple biopsies of the fistulous tracks or perianal mass are necessary to establish the diagnosis. An accurate staging of the neoplasm, using endorectal ultrasound, NMR or CT scans is needed to plan the appropriate treatment. Recent studies have shown that locally advanced anal adenocarcinomas could benefit from pre or postoperative chemoradiation therapy. However, an accurate and complete removal of the tumor, which usually entails abdominoperineal resection, is often necessary to achieve radicality. Despite new therapy protocols, the prognosis of mucinous adenocarcinoma is still poor, mostly due to its advanced nature at the time of diagnosis. This reinforces the importance of biopsy of all perianal abscesses and fistulas for early detection and treatment.

The methylator phenotype in microsatellite stable colorectal cancers is characterized by a distinct gene expression profile.

The CpG island methylator phenotype (CIMP) in colorectal tumours can be recognized by an increased frequency of aberrant methylation in a specific set of genomic loci. Because of the strong association of CIMP with high microsatellite instability (MSI-H), the identification of CIMP+ tumours within microsatellite stable (MSS) colorectal cancers may not be straightforward. To overcome this potential limitation, we have built an improved seven-locus set of methylation markers that includes CACNA1G, IGF2, RUNX3, HTR6, RIZ1, MINT31, and MAP1B. This new set of CIMP markers revealed a bimodal distribution of methylation frequencies in a group of 95 MSS colorectal cancers, which allowed a clearer separation between CIMP classes. Correlation of MSS CIMP+ tumours with bio-pathological traits revealed significant associations with location to the proximal colon, mucinous histology, BRAF mutation, and chromosomal stability. A potential trend towards an adverse prognosis of CIMP+ cases was associated with the high frequency of BRAF mutations present within this cohort of tumours. Microarray analysis revealed that CIMP+ tumours are characterized by a unique expression profile, a result that confirms that CIMP+ tumours represent a truly distinct molecular class within MSS colorectal cancers.

[Expression of protein p53 in the adenoma-colorectal carcinoma sequence]. / Espressione della proteina p53 nella sequenza adenoma-carcinoma del colon-retto.

To further evaluate the role of the p53 gene in the development of colorectal carcinoma we examined by immunohistochemistry p53 protein expression in a series of 136 colorectal adenomas, 25 adenomas containing early invasive carcinoma (pT1) and 160 advanced adenocarcinomas (pT3-pT4). p53 overexpression was detected in 22% of adenomas, 64% of adenomas with invasive carcinoma and 60% of advanced adenocarcinomas. In colorectal adenomas p53 expression was related to tumour size (P = 0.0013), histologic type (P < 0.0001) and grade of dysplasia (P < 0.0001). Only 7.5% of adenomas with low grade dysplasia were found to be p53 positive, whereas 73.3% of adenomas with high grade dysplasia demonstrated p53 overexpression. Most p53 positive adenomas and adenomas with invasive carcinoma showed intratumoural heterogeneity of p53 immunoreactivity. Conversely advanced adenocarcinomas were always uniformly p53 positive or negative. Our data show that p53 protein overexpression occurs at the transition from low grade dysplasia to high grade dysplasia, indicating a likely role for the p53 gene in the conversion of benign adenoma to malignant carcinoma.

[Pathological factors involved in lymph node status determination in colorectal carcinoma: analysis of 166 cases with long-term follow-up]. / Fattori patologici inerenti la determinazione dello stato linfonodale nel carcinoma colorettale: analisi di 166 casi con follow-up a lungo termine.

Lymph node status has great clinical importance in the management of patients with colorectal cancer. Several pathologic factors may affect the accuracy of nodal status assessment in this tumor type. The aim of the present study was to evaluate, in a series of 166 stage II and stage III colorectal adenocarcinomas, the following pathologic parameters: number of lymph nodes recovered and examined, number of lymph nodes with metastases, and number of tumor nodules (TNs) in the perirectal or pericolic adipose tissue greater or smaller than 3 mm in diameter (TNs > 3 mm and TNs < 3 mm, respectively). The prognostic significance of these parameters, as well as of other histopathologic variables, was determined using univariate and multivariate survival analyses. Our results indicate that the examination of a small number of regional lymph nodes may result in understaging of tumors classified as pN0 (stage II). In addition, our data suggest that TNs > 3 mm and TNs < 3 mm represent distinct pathologic entities. TNs > 3 mm should be considered the prognostic equivalent of lymph node metastases as recommended by the 1997 TNM classification. In contrast, TNs < 3 mm probably originate by intravascular or perivascular tumor extension. Their presence is associated with adverse clinical outcome in stage III patients, regardless of the number of lymph node metastases.

[Evaluation of prognostic parameters in colorectal carcinoma. II. Ploidy determination with flow cytometry]. / Valutazione di parametri prognostici nel carcinoma del colon-retto. II.Ploidia mediante citometria a flusso.

The prognostic value of DNA ploidy in large bowel cancer is still controversial. In the present investigation we have evaluated the nuclear DNA content in 123 colorectal adenocarcinomas by flow cytometry using multiple frozen tumour samples. Thirty-three (26.8%) carcinomas were classified as diploid and 90 as aneuploid (73.2%). Presence of DNA aneuploidy was found to be unrelated to age and sex of patients, tumour stage and grade of differentiation, as well as to several other histopathological variables. However, multiploid tumours (20/123, 16.3%) resulted to be more frequently in advanced stages of disease (stages III and IV, P < 0.025) and more often showed unfavourable histopathological features, especially an infiltrating pattern of growth (P < 0.05), compared to diploid and single aneuploid carcinomas. Nuclear DNA content was found to be closely related to tumour site. Carcinomas of the proximal colon were more frequently diploid (P < 0.005) and more often displayed a DI < or = 1.20 (P < 0.001) than tumours of the distal colon. Nuclear DNA content was also found to be related to tumour type. In fact, a high proportion (66.7%) of mucinous carcinomas showed DI values < or = 1.20; conversely only 31.4% of nonmucinous adenocarcinomas had a DI < or = 1.20 (P < 0.01). Intratumoural heterogeneity in nuclear DNA content was found in 23% of cases. These results seem to suggest that the DNA ploidy pattern probably reflects different genetic mechanisms involved in the development of carcinomas in the proximal and distal colon. Furthermore our data support the hypothesis that mucinous carcinoma represents a distinct clinicopathologic entity, possibly related to pathogenetic factors different from those acting in the majority of nonmucinous adenocarcinomas. Finally, the analysis of multiple tissue samples taken from different areas of each tumour is necessary to assess carefully the DNA ploidy pattern of large bowel carcinomas.

Sporadic colorectal adenocarcinomas with high-frequency microsatellite instability.

BACKGROUND: Widespread microsatellite instability (MSI) occurs in nearly 15% of sporadic colorectal cancers. Large bowel carcinomas with high-frequency MSI (MSI-H) (instability at > or = 30% of microsatellite loci) are believed to display distinctive pathologic features and to behave less aggressively than microsatellite-stable (MSS) tumors and carcinomas with low-frequency MSI (MSI-L) (instability at < 30% of microsatellite loci). The aim of the current study was to accurately define the clinicopathologic and biologic features of MSI-H sporadic colorectal carcinomas. METHODS: MSI status was evaluated in 216 large bowel adenocarcinomas using polymerase chain reaction (PCR) and 6 microsatellite markers. Tumors that showed instability with at least two microsatellite markers were classified as MSI-H, whereas the other tumors were classified as MSI-L (instability at one locus) or MSS (no instability). Expression of p53, hMLH1, and hMSH2 gene products was determined by immunohistochemistry, and DNA ploidy pattern was determined by flow cytometry. The prognostic significance of MSI status was assessed by univariate and multivariate survival analyses. RESULTS: The significantly different pathologic features of MSI-H carcinomas were proximal location; large size; mucinous and medullary histotype; poor differentiation; expanding pattern of growth; more frequent Crohn-like conspicuous lymphoid reaction; and low incidence of extramural vein invasion. Most MSI-H tumors were DNA diploid (33 of 40 tumors; 82.5%) and p53 negative (34 of 44 tumors; 77.3%). Conversely, DNA aneuploidy and p53 overexpression were observed in 82.3% (130 of 158 tumors; P < 0.0001) and 54.1% (93 of 172 tumors; P = 0.0002) of MSI-L/MSS tumors, respectively. Loss of hMLH1 or hMSH2 expression was detected in a high fraction of MSI-H carcinomas (86. 0%). Patients with MSI-H tumors showed a better clinical outcome than patients with MSI-L/MSS tumors (P = 0.0017). Furthermore, in multivariate analysis that included conventional clinicopathologic parameters, MSI status, and p53 expression as covariates, MSI status was a significant independent prognostic indicator of disease specific survival. CONCLUSIONS: Assessment of MSI status is an essential step in the genetic characterization of large bowel carcinomas and identifies a subset of tumors with distinct clinical, pathologic, and biologic features.

[Clinico-pathological features and biological characterization of mucoid colorectal carcinoma]. / Aspetti clinico-pathologici e caratterizzazione biologica del carcinoma mucoide del colon-retto.

The clinical, pathological and biologic features of 79 mucinous colorectal carcinomas were compared with those of 602 non-mucinous adenocarcinomas. The two groups did not show appreciable differences in patients' age, stage distribution, extent of lymph node involvement, grade of differentiation, pattern of growth and venous invasion. Mucinous carcinomas occurred more frequently among female patients (P < 0.05) and in the proximal colon (P < 0.01). Moreover, mucinous carcinomas more often demonstrated origin within villous adenomas (P < 0.0001) and lacked pronounced peritumoural lymphocytic infiltration (P < 0.001). A strong association was found between tumour type and flow cytometric nuclear DNA content. A high proportion of mucinous carcinomas showed DNA index (DI) values < or = 1.20 (26/38, 68.4%); conversely only 103 of 322 (32%) non-mucinous carcinomas had a DI < or = 1.20 (P < 0.0001). In addition mucinous carcinomas were characterized by infrequent p53 overexpression (4/21, 19% versus 120/183, 65.6%; P < 0.001) and higher levels of proliferative activity (P < 0.0001) compared to non-mucinous adenocarcinomas. Our data support the hypothesis that mucinous carcinoma represents a distinct clinicopathologic and genetic entity.

Prognostic significance of DNA ploidy in patients with stage II and stage III colon carcinoma: a prospective flow cytometric study.

BACKGROUND: The prognostic value of flow cytometric DNA ploidy in colorectal carcinoma has not been defined clearly. Most previous studies were conducted retrospectively using archival formalin fixed, paraffin embedded tumor samples. Conversely, few data on prospective studies employing fresh or frozen tissue specimens are available. There is general agreement that fresh/frozen material is more reliable than paraffin embedded tissue for DNA ploidy analysis by flow cytometry. METHODS: In the current investigation we evaluated the prognostic significance of nuclear DNA content in a prospective series of 191 patients with curatively resected TNM Stage II (n = 107) or Stage III (n = 84) sporadic colon carcinomas. DNA ploidy status was assessed by flow cytometry utilizing multiple frozen tumor samples. Mean follow-up in surviving patients was 48.5 months (median, 46.9 months; range, 29-77 months). The Cox proportional hazards model was used to adjust for several clinical and pathologic covariates. RESULTS: Of the 191 carcinomas examined, 47 (24.6%) were classified as DNA diploid and 144 (75.4%) as DNA aneuploid. DNA ploidy pattern was significantly related to tumor site (P < 0.0001), histologic type (P = 0.0002), and grade of differentiation (P = 0.009), but not to other clinical and pathologic variables. Patients with DNA diploid tumors showed a better disease free (P = 0.013) and overall survival (P = 0.021) than patients with DNA aneuploid adenocarcinomas. In particular, patients with Stage II DNA diploid tumors (n = 30) had an excellent clinical outcome, with an overall 5-year survival rate of 97%. When patients were analyzed according to the anatomic site of the tumor, a significant relationship between DNA ploidy status and disease free and overall survival was observed in the group of patients with carcinomas of the proximal colon (n = 84) (P = 0.004 and P = 0.002, respectively), but not among patients whose tumors were sited distally to the splenic flexure (n = 107). In multivariate analysis, nuclear DNA content was demonstrated to be an independent prognostic variable for both disease free and overall survival. Furthermore, in the group of patients with tumors of the proximal colon, DNA ploidy pattern was the single most important prognostic factor. CONCLUSIONS: Our results confirm that flow cytometric DNA ploidy status is a significant and independent prognostic factor in patients with colon carcinoma. These findings may have clinical implications for the management of affected patients, especially those with Stage II disease.

Chromosome 18q allelic loss and prognosis in stage II and III colon cancer.

The prognostic significance of chromosome 18q allelic loss was evaluated in a series of 118 patients with curatively resected TNM stage II or stage III colon cancer. Chromosome 18q status was determined on frozen tumour samples, using microsatellite markers and the polymerase chain reaction (PCR). Mean follow-up in surviving patients was 75.9 months. Chromosome 18q allelic loss was significantly related to tumour site, extramural venous invasion, flow cytometric nuclear DNA content and p53 protein expression. Patients whose tumour had no evidence of chromosome 18q allelic loss showed a better disease-free and overall survival than patients whose tumour demonstrated 18q allelic loss. When patients were stratified by tumour stage, a significant survival advantage for patients whose tumour had no allelic loss on chromosome 18q was observed in stage II as well as in stage III disease. In particular, patients with stage II disease whose tumour had no chromosome 18q allelic loss demonstrated an excellent clinical outcome, with a 5-year disease-free survival rate of 96%. In contrast, the 5-year disease-free survival rate of patients with stage II disease and chromosome 18q allelic loss was only 54%. In multivariate analysis, status of chromosome 18q was the only significant independent prognostic factor for both disease-free and overall survival. These results indicate that assessment of chromosome 18q status provides relevant prognostic information in colon cancer and might be employed in the selection of patients for adjuvant therapy.

Genetic progression in microsatellite instability high (MSI-H) colon cancers correlates with clinico-pathological parameters: A study of the TGRbetaRII, BAX, hMSH3, hMSH6, IGFIIR and BLM genes.

Colon carcinomas with microsatellite mutator phenotype exhibit specific genetic and clinico-pathological features. This report describes the analysis of 63 "microsatellite instability-high" (MSI-H) tumors for the presence of mutations in microsatellites located in the coding regions (CDRs) of 6 genes: TGFbetaRII, BAX, hMSH3, hMSH6, IGFIIR, and BLM. The following frequencies of mutations were detected: TGFbetaRII (70%), BAX (54%), hMSH3 (36.5%), IGFIIR (22%), hMSH6 (17.5%), and BLM (16%). The overall picture revealed combinations of mutations suggestive of a progressive order of accumulation, with mutations of TGFbetaRII and BAX first, followed by frameshifts in hMSH3, hMSH6, IGFIIR, and BLM. Correlations with 12 clinico-pathological parameters revealed that tumors with frameshifts in 1 or 2 CDRs were significantly better differentiated than tumors with frameshifts in more than 2 CDRs. We also found that mutations in the hMSH3 gene were significantly associated with decreased wall invasiveness and aneuploidy, and frameshifts in the BLM gene were significantly associated with the mucinous histotype. A trend toward an association between hMSH3 and IGFIIR with the medullary and conventional adenocarcinoma histotypes, respectively, was seen. Our results strengthen the concept that mutations in target genes have a role in the tumorigenic process of MSI-H tumors, and indicate that frameshifts in microsatellites located in CDRs occur in a limited number of combinations that could determine distinct clinico-pathological traits.

Microsatellite instability and high content of activated cytotoxic lymphocytes identify colon cancer patients with a favorable prognosis.

Colorectal cancers with high-frequency microsatellite instability show peculiar clinicopathological features and a favorable clinical outcome. We investigated whether the improved prognosis for these cancers is related to the content of activated cytotoxic intraepithelial T lymphocytes. Microsatellite instability and the amount of activated cytotoxic lymphocytes were analyzed according to clinicopathological features, survival, and disease recurrence in 109 right-sided colon carcinomas from 245 consecutive patients with stage II/III colon cancer that underwent radical surgery. High-frequency microsatellite instability was found in 43% of stage II/III proximal colon cancers and was associated with significantly higher numbers of activated cytotoxic lymphocytes. High-frequency microsatellite instability, as well as the content of intratumoral-activated cytotoxic T lymphocytes correlated with improved overall and disease-free survival, particularly in patients with stage III tumors. Multivariate analysis revealed that patients with both features had a risk of death and relapse markedly lower than that associated with microsatellite status or intratumoral cytotoxic lymphocytes separately. The presence of local cytotoxic immune responses is probably the major determinant of the good clinical course of patients with microsatellite unstable colon cancer. Furthermore, high-frequency microsatellite instability coupled with a high content of intratumoral cytotoxic lymphocytes may identify a subset of colon cancer patients with a favorable clinical outcome, particularly in stage III disease.

Microsatellite instability in multiple colorectal tumors.

Tumor multiplicity is a hallmark of hereditary cancers: in the colon-rectum multiple tumors represent 5-10% of all colorectal cancer cases. A portion of these cases belongs to hereditary non-polyposis colorectal cancer (HNPCC), a genetic cancer syndrome due to mismatch repair (MMR) gene mutations, phenotypically expressed as microsatellite instability (MSI); the majority of multiple tumors, however, is apparently without any family history. We analyzed 78 (38 synchronous and 40 metachronous) neoplasms from 37 patients with multiple tumors of the large bowel, both HNPCC and sporadic, with the aim of identifying a common genetic basis in multiple tumors. DNA was extracted from normal and cancerous formalin-fixed tissue and was analyzed for MSI using 6 markers. Tumors showing MSI in at least 2 of 6 microsatellite loci were defined as MSI(+). The overall number of MSI(+) tumors was 22 (28.2% of the total). A significant difference in the rate of MSI(+) between HNPCC and sporadic tumors was observed (85% vs. 17%). In the same patients, the MSI phenotype of synchronous tumors (both HNPCC and sporadic) tended to be more concordant than that of the metachronous ones. The higher frequency of MSI in HNPCC than in sporadic tumors, even when multiple, suggests that the involvement of MMR genes in the pathogenesis of the sporadic cases may be uncommon, thus confirming that screening for MSI in multiple colorectal tumors could be a useful tool in the identification of HNPCC in the general population.