Mosaic partial deletion of the PTEN gene in a patient with Cowden syndrome

Cowden syndrome is an autosomal dominant condition caused by pathogenic mutations in the phosphatase and tensin homolog (PTEN) gene. Only a small proportion of identified pathogenic mutations have been reported to be large deletions and rearrangements. We report on a female patient with a previous history of breast ductal carcinoma in situ who presented to our institution for management of gastrointestinal hamartomatous polyposis. Although several neoplastic predisposition syndromes were considered, genetic evaluation determined that the patient met clinical diagnostic criteria for Cowden syndrome. Array-based comparative genomic hybridization was performed and revealed a mosaic partial deletion of the PTEN gene. Follow-up clinical history including bilateral thyroid nodules, dermatological findings, and a new primary "triple-negative" adenocarcinoma of the contralateral breast are discussed. We highlight the need for recognition and awareness of mosaicism as it may provide an explanation for variable phenotypic presentations and may alter the genetic counseling risk assessment of affected individuals and family members.

Results of a prospective thyroid ultrasound screening program in adenomatous polyposis patients

BACKGROUND

Patients with adenomatous polyposis may be at increased risk for developing thyroid cancer (TC). However, screening guidelines for TC in these patients are not well established.

METHODS

Patients with a diagnosis of familial adenomatous polyposis, attenuated familial adenomatous polyposis, and gene mutation-negative adenomatous polyposis enrolled in our Hereditary Colorectal Cancer Family Registry were eligible for a screening thyroid ultrasound (US). Findings were reviewed by the study endocrinologist and intervention and/or follow-up determined.

RESULTS

Fifty patients underwent screening thyroid US. Thirty-four (68%) patients had abnormal findings on US, including 27 (79%) with thyroid nodules. In 7 patients, US-detected thyroid nodules met established criteria for fine-needle aspiration. Of the 6 patients who underwent fine-needle aspiration, 2 (4%) were diagnosed with papillary TC. Both of these patients were female.

CONCLUSIONS

A large proportion of adenomatous polyposis patients will have abnormal results on thyroid US, including suspicious-appearing thyroid nodules that when biopsied are malignant. Female patients have an apparently greater risk of developing TC. Polyposis patients, especially women, should be offered participation in a thyroid US screening program.

Endoluminal high-dose-rate brachytherapy for early stage and recurrent esophageal cancer in medically inoperable patients

PURPOSE

The management of superficial primary and recurrent esophageal cancer (EC) in medically inoperable patients is complex. Endoluminal high-dose-rate (HDR) brachytherapy has shown mixed results in terms of toxicity and local control. In this study, we examined the outcomes and toxicities in a set of patients with superficial primary and recurrent EC treated with a consistent HDR technique.

METHODS AND MATERIALS

Between 8/2008 and 7/2011, 14 patients were treated with HDR intraluminal brachytherapy, 10 (71.4%) with recurrent disease, and 4 (28.6%) with previously unirradiated lesions. Patients received three weekly fractions to a median dose of 12 Gy (range, 10-15 Gy); dose was prescribed to 7-mm median depth with mucosal dose limited to 8-10 Gy using a 12-14-mm applicator.

RESULTS

Median followup was 15.4 months. Overall freedom from failure (OFFF) and overall survival (OS) at 18 months were 30.8% (95% confidence interval [CI]: 5.2, 56.4) and 72.7% (95% CI: 45.3, 100), respectively. For patients with recurrent disease, OFFF and OS at 18 months were 11.1% (95% CI: 0, 32.1) and 55.6% (95% CI: 15.4, 95.8), respectively. For patients with previously unirradiated disease, OFFF and OS at 18 months were 75.0% (95% CI: 31.6, 100) and 100.0%, respectively. Eight (57.1%) patients had Grade 1 acute adverse effects; 6 (42.9%) patients had chronic Grade 1 adverse effects; 1 (7.1%) patient developed Grade 2 stricture. Grade 3 tracheoesophageal fistula occurred in 1 (7.1%) patient. One patient died before completion of treatment of unrelated causes.

CONCLUSIONS

HDR endoluminal brachytherapy is a well-tolerated treatment for superficial primary and recurrent EC in medically inoperable patients.

Patients with colorectal and renal cell carcinoma diagnoses appear to be at risk for additional malignancies

Patients with colorectal cancer (CRC) and renal cell carcinoma (RCC) may be at risk for additional primary malignancies. A review of 101 patients with these concurrent diagnoses was performed. Forty-two percent of patients had 1 or more additional malignancies; none appeared to be associated with Lynch syndrome (LS). This suggests the need for careful follow-up in these patients and further study.

BACKGROUND

Small studies have demonstrated that patients who have both colorectal and renal cell carcinoma may be at increased risk for the development of additional malignancies. A possible genetic basis has been suggested. Our study describes the clinicopathologic features of these patients and clarifies the relationship of this cohort with Lynch syndrome (LS).

METHODS

Patients with primary CRC and RCC treated at our institution were identified. Medical records were reviewed for demographic and clinical information. Immunohistochemical staining for mismatch repair (MMR) proteins was performed on tumor tissue when possible.

RESULTS

During the study period, 24,642 patients were treated for CRC and 7,366 were treated for RCC at our institution. One hundred seventy-nine patients had both diagnoses, with 101 patients eligible for inclusion in our cohort. Tumors were typically early stage. The 2 cancers presented as synchronous lesions in 42% of patients. Thirty-two patients had 1 additional primary malignancy, 7 patients had 2 additional primary malignancies, and 3 patients had 3 additional primary malignancies. No patient had a family history that met the Amsterdam II criteria (AC) for LS, but 50% had family members with 1 malignancy. One of 10 colorectal tumors analyzed for the absence of MMR protein expression demonstrated the absence of MSH6, but the corresponding RCC demonstrated intact expression of all 4 MMR proteins.

CONCLUSION

It is rare for patients to be diagnosed with both CRC and RCC. The clinicopathologic features of this cohort and the results of immunohistochemical analysis performed on a sample of these patients do not suggest LS. However, the high rate of additional carcinomas suggests a need for careful follow-up. Multicenter longitudinal studies are warranted to further understand the natural history and possible genetic basis for this entity.

Endoscopic management of complete colonic obstruction

A patient with metastatic rectal cancer underwent a diverting transverse loop colostomy due to rectal obstruction. 16 months later, he underwent a low anterior resection to resect his rectal cancer along with reversal of his transverse colostomy, and creation of a temporary loop ileostomy. Six months later, he was brought to the operating room for closure of his ileostomy. Post-operatively, the patient developed nausea, vomiting, and abdominal distention and imaging revealed a large bowel obstruction, confirmed by colonoscopy. The patient refused surgical diversion and a cecostomy tube was placed for decompression. After maturation of the cecostomy fistula, a rendezvous colonoscopy was performed, retrograde through the rectum and antegrade through the cecostomy fistula. The obstructing mucosa was traversed and the site of obstruction was balloon dilated, relieving the obstruction endoscopically.

Systematic immunohistochemistry screening for Lynch syndrome in early age-of-onset colorectal cancer patients undergoing surgical resection

BACKGROUND

Lynch syndrome (LS), defined by a deleterious (pathogenic) germline mutation in a mismatch repair (MMR) gene, is characterized by early age-of-onset colorectal cancer (CRC). Because clinical criteria for LS, such as the Amsterdam II Criteria, may miss cases, reflex tumor tissue testing of all CRC patients for LS has been proposed. Our study describes the impact of routine immunohistochemistry (IHC) analysis of tumor tissue for loss of MMR protein expression in early age-of-onset CRC patients undergoing resection.

STUDY DESIGN

A prospective institutional program was established to perform IHC analysis on all early age-of-onset (≤50 years) CRC patients undergoing resection. Patients with abnormal IHC analysis were referred to the Clinical Genetics Service for further evaluation. The study cohort excluded patients with other polyposis syndromes and inflammatory bowel disease.

RESULTS

IHC was performed on 198 patients from July 2006 to June 2010. The median age was 42.8 years (range 23.1 to 50.6 years). Abnormal IHC was reported in 38 (19.1%) patients, and 22 (57.8%) with abnormal IHC analysis had germline genetic testing. Seventeen (77.2%) had an alteration detected in an MMR gene: 10 were known to be deleterious mutations and 7 were variants of uncertain significance. Overall, LS was detected in 5.1% of patients. Only 2 of the 10 (20%) with a deleterious mutation actually met the Amsterdam II Criteria.

CONCLUSIONS

Reflex IHC testing for LS on early age-of-onset CRC patients undergoing resection is feasible at the institutional level. This strategy identifies a substantial number of LS patients who would have been missed if genetic testing was based on the Amsterdam II Criteria alone.

Hepatitis C and non-Hodgkin lymphoma: the clinical perspective

Hepatitis C virus (HCV) is a commonly transmitted infection that has both hepatic and extrahepatic repercussions. These range from the inflammatory to the oncologic with an undisputed link to hepatitis, liver cirrhosis, and hepatocellular carcinoma. Its role in the development of B cell non-Hodgkin lymphoma (B-NHL) is becoming better understood, leading to opportunities for research, therapy, and even prevention. Research in the field has progressed significantly over the last decade, with the number of patients diagnosed with HCV and B-NHL rising incrementally. It is therefore becoming crucial to fully understand the pathobiologic link of HCV in B cell lymphomagenesis and its optimal management in the oncologic setting.

Carcinomatosis is not a contraindication to enteral stenting in selected patients with malignant gastric outlet obstruction

BACKGROUND

Endoscopically inserted self-expandable metal stents (SEMSs) are used to palliate malignant gastric outlet obstruction (GOO). Peritoneal disease is considered a relative contraindication to SEMS placement given the risk of multifocal obstruction.

OBJECTIVE

To evaluate the success of SEMSs placed in patients with GOO with carcinomatosis.

DESIGN

Retrospective review of patients who underwent SEMS placement for malignant GOO.

SETTING

Large, urban cancer center.

PATIENTS

A total of 215 patients who were scheduled for SEMS placement for GOO.

INTERVENTIONS

SEMS placement.

MAIN OUTCOME MEASUREMENTS

Technical success, clinical success, early and late SEMS failure, and complications.

RESULTS

Technical success was achieved in 192 of 201 patients (95.5%). Of the 9 patients who did not achieve technical success, 6 had carcinomatosis. Among the 116 patients (60%) with carcinomatosis, clinical success was achieved 94 of them (81%). Of these 94 patients, 17 (18%) required reinterventions: 4 for early SEMS failure and 13 for late SEMS failure. Among the 76 patients (40%) without carcinomatosis, clinical success was achieved in 64 of them (84%). Of these 64 patients, 17 (27%) required reinterventions: 4 for early SEMS failure and 13 for late SEMS failure. Complication rates were similar for both groups.

LIMITATIONS

This was a retrospective review with experienced clinicians selecting patients whom they thought would benefit from SEMS placement.

CONCLUSIONS

This is the first study to evaluate the effect of carcinomatosis on the technical and clinical success of SEMSs in the palliation of malignant GOO. We found clinical outcomes comparable to those without peritoneal disease. Carcinomatosis should not be considered a contraindication to SEMS placement in selected patients with malignant GOO.

How to manage a patient with multiple adenomatous polyps

Adenomatous polyps are found on screening colonoscopy in 22.5% to 58.2% of the adult population and therefore represent a common problem. Patients with multiple adenomatous polyps are of unique interest because a proportion of these patients have an inheritable form of colorectal cancer. This article discusses the history and clinical features, genetic testing, surveillance, and treatments for the condition.

Endoscopic ultrasound can improve the selection for laparoscopy in patients with localized gastric cancer

BACKGROUND

The majority of newly diagnosed patients with gastric cancer have disease that is not resectable because of local extension or metastatic (M1) disease. Laparoscopy is a recommended staging evaluation to identify occult peritoneal metastatic disease. We determined if endoscopic ultrasound (EUS) could improve the selection of patients for laparoscopy.

STUDY DESIGN

Gastric cancer patients being screened for a preoperative chemotherapy clinical trial were prospectively examined. Patients underwent standard preoperative assessment. Those without obvious metastatic disease were referred for EUS and laparoscopy. EUS divided patients into risk categories for metastatic disease: low risk (T1-2, N0) and high risk (T3-4, N+, or both). Laparoscopy categories were M1 and M0. The ability of EUS to predict subradiographic peritoneal metastatic disease was evaluated.

RESULTS

Ninety-four patients were studied. The majority were EUS high risk (72%). Occult metastatic disease was identified in 19 patients, 18 of whom had high-risk EUS stage. The yields of identifying M1 disease by laparoscopy in EUS high- and low-risk patients were 25% (95% CI, 15% to 37%) and 4% (95% CI, 0.1% to 20%), respectively. The negative predictive value of low-risk EUS for laparoscopy and pathologic M0 was 96% (exact 95% CI, 80% to 100%).

CONCLUSIONS

This study suggested that laparoscopy can be avoided in patients with EUS early-stage gastric cancer. Patients with more advanced disease are at higher risk of occult peritoneal disease and require laparoscopy. Validation with greater numbers is warranted, but, based on these data, we propose a new staging algorithm allowing EUS low-risk patients to proceed directly to resection.

Positron Emission Tomography Detection of Distant Metastatic or Synchronous Disease in Patients with Locally Advanced Rectal Cancer Receiving Preoperative Chemoradiation

BACKGROUND

Patients with locally advanced rectal cancer may present with synchronous distant metastases. Choice of optimal treatment--neoadjuvant chemoradiation versus systemic chemotherapy alone--depends on accurate assessment of distant disease. We prospectively evaluated the ability of [18F]fluorodeoxyglucose ([18F]FDG) positron emission tomography (PET) to detect distant disease in patients with locally advanced rectal cancer who were otherwise eligible for combined modality therapy (CMT).

METHODS

Ninety-three patients with locally advanced rectal cancer underwent whole-body [18F]FDG PET scanning 2-3 weeks before starting CMT. Sites other than the rectum, mesorectum, or the area along the inferior mesenteric artery were considered distant and were divided into nine groups: neck, lung, mediastinal lymph node (LN), abdomen, liver, colon, pelvis, peripheral LN, and soft tissue. Two nuclear medicine physicians blinded to clinical information used PET images and a five-point scale (0-4) to determine certainty of disease. A score greater than 3 was considered malignant. Confirmation was based on tissue diagnosis, surgical exploration, and subsequent imaging.

RESULTS

At a median follow-up of 34 months, the overall accuracy, sensitivity, and specificity of PET in detecting distant disease were 93.7%, 77.8%, and 98.7% respectively. Greatest accuracy was demonstrated in detection of liver (accuracy = 99.9%, sensitivity = 100%, specificity = 98.8%) and lung (accuracy = 99.9%, sensitivity = 80%, specificity = 100%) disease; PET detected 11/12 confirmed malignant sites in liver and lung. A total of 10 patients were confirmed to have M1 stage disease. All 10 were correctly staged by pre-CMT PET; abdominopelvic computed tomography (CT) scans accurately detected nine of them.

CONCLUSION

Baseline PET in patients with locally advanced rectal cancer reliably detects metastatic disease in liver and lung. PET may play a significant role in defining extent of distant disease in selected cases, thus impacting the choice of neoadjuvant therapy.

Single-amplicon MSH2 A636P mutation testing in Ashkenazi Jewish patients with colorectal cancer: role in presurgical management

OBJECTIVE

This study summarizes our initial experience with prospective, single-amplicon (mutation-specific) A636P testing in Ashkenazi Jewish patients at risk for Hereditary Nonpolyposis Colorectal Cancer (HNPCC).

SUMMARY BACKGROUND DATA

We previously described a founder mutation, MSH2*1906G >C (A636P) that causes HNPCC in 8/1345 (0.59%) of Ashkenazim with colorectal cancer. The mutation was more common in Ashkenazim diagnosed at <or=40 years (7%).

METHODS

Twenty-seven Ashkenazi probands at risk for HNPCC were ascertained. Single-amplicon A636P testing was performed on 21 by polymerase chain reaction of exon 12 of MSH2, followed by direct DNA sequencing. Mutational analysis of the entire open reading frame of MLH1 and MSH2 was performed on 7 by PCR of each exon, followed by heteroduplex analysis using denaturing high-performance liquid chromatography and direct sequencing of exons with variant chromatographs. One patient received both studies,

RESULTS

The A636P mutation was detected in 3/21 (14%) prospectively evaluated patients using single amplicon testing. In 6 patients, the entire open reading frame of MLH1 and MSH2 was analyzed, and 1 additional A636P carrier and 2 carriers of previously unrecognized mutations were identified. The A636P mutation was present in 2 patients who met Amsterdam criteria and in 2 patients who did not.

CONCLUSIONS

Although rare in the general population, A636P mutations are found at increased frequency in Ashkenazim with a personal or family history of colorectal or other HNPCC-associated cancers. This inexpensive and rapid approach may be useful preoperatively in helping determine the extent of colon resection for a subset of patients.

Combined CT colonography and 18F-FDG PET of colon polyps: potential technique for selective detection of cancer and precancerous lesions

OBJECTIVE

The purpose of this study was to determine the feasibility of imaging the colon with fused CT colonography (CTC) and 18F-FDG PET and to correlate the findings with the histologic features of polyps.

SUBJECTS AND METHODS

Eighteen patients with suspected colorectal polyps enrolled in this prospective study. Before colonoscopy, 17 of the patients underwent a combination of FDG PET and CTC. CTC consisted of 4-MDCT merged with PET. PET of the abdomen and pelvis was performed after each CTC scan. One radiologist and one nuclear medicine physician in consensus analyzed PET and CTC fusion data. PET standard uptake value was correlated with the findings at histologic examination of polyps. Patient feasibility was defined as the ability to tolerate prolonged scanning with good colonic distention. Technical feasibility was determined by how closely anatomically matched polyps overlapped on fusion images.

RESULTS

Seventeen of 18 patients tolerated scanning. Eighty-five percent of colon segments were optimally distended. Twenty-three of 27 FDG-avid polyps measuring 10 mm or more had excellent overlap at fusion imaging. PET depicted 23 of 39 premalignant polyps and even showed increased tracer activity associated with four small tubular adenomas (4-6 mm). Sixteen benign polyps (10-25 mm) were not depicted on PET. All nine cases of cancer (tumors measuring 11-60 mm) were detected with both PET and CTC. The standard uptake value of malignant tumors ranged from 4 to 20 (mean, 9). However, six benign flat polyps did not exhibit FDG avidity.

CONCLUSION

The novel combination of CTC and PET was feasible in 17 of 18 patients and allowed excellent image correlation in 23 of 27 proven polyps measuring 10 mm or more on PET-CTC fusion. This technique shows promise in accurate anatomic correlation of both malignant and premalignant lesions evaluated with FDG PET.

CT colonography features of sigmoid diverticular disease

OBJECTIVE

The objective of this study is to assess the sigmoid distensibility during CT colonography (CTC) in patients with diverticular disease.

METHODS

Consecutive patients without a history of pelvic radiation or neoplasms underwent 150 CTC. Three radiologists in consensus evaluated axial images for colonic distention, luminal diameters (mm), diverticula, and muscular thickening.

RESULTS

The minimum colon diameter in patients with muscular thickening was significantly smaller, irrespective of the presence of diverticula (P=.009).

CONCLUSION

Muscular thickening with diverticular disease was associated with significantly less sigmoid colon distension.

A636P testing in Ashkenazi Jews

Hereditary nonpolyposis colorectal cancer (HNPCC) is an autosomal dominantly inherited colorectal cancer syndrome attributable to mutations in one of several DNA mismatch repair genes, most commonly MLH1 and MSH2 . In certain populations, founder mutations account for a substantial portion of HNPCC. In this report we summarize the literature and our personal experience testing for a specific founder mutation in the Ashkenazi Jewish population, MSH2*1906G > C , also known as A636P. Although rare in the general population, the A636P mutation is detected in up to 7% of Ashkenazi Jewish patients with early age-of-onset colorectal cancer, and may account for up to one third of HNPCC in the Ashkenazi Jewish population. In addition, we summarize our initial experience with a prospective A636P testing protocol aimed at Ashkenazi Jewish patients at high or intermediate risk for harboring the A636P mutation.

Value of immunohistochemical detection of DNA mismatch repair proteins in predicting germline mutation in hereditary colorectal neoplasms

The utility of immunohistochemistry (IHC) as a screening method for the identification of persons with mutations in the DNA mismatch repair (MMR) genes in hereditary nonpolyposis colorectal cancer (HNPCC) remains to be defined. In this study, we analyzed the value of IHC versus that of microsatellite instability (MSI) testing in predicting mutation status of the MLH1, MSH2, and MSH6 genes in colorectal carcinomas and adenomas, and explored the frequency and significance of immunohistochemical staining variability. The study samples included 83 carcinomas and 29 adenomas derived from 110 patients who had strong family histories of colorectal cancer. Our results showed that IHC correctly predicted MSI status in 76% of the cases with a specificity of 100%. The overall sensitivity of IHC in predicting a germline mutation was 79% (30 of 38) with a specificity of 89% (48 of 54), whereas that of MSI testing was 97% (30 of 31) with a specificity of 83% (35 of 42). Six of 31 analyzable cases that had a disease-causing mutation and exhibited MSI showed normal IHC. The lower sensitivity of IHC was caused mainly by its low sensitivity in detecting MLH1 gene mutation (4 of 9). Coexisting adenomas and carcinomas observed in the same slide (n=12) showed a similar or identical staining pattern for all three proteins. No significant difference was detected in the sensitivity of IHC or MSI in detecting a germline mutation between isolated adenomas and carcinomas. In IHC-positive cases, heterogeneous staining was noted in 30% to 40% of the cases with the three different antibodies, and cytoplasmic staining in 5% to 13%. Weak IHC (defined as positive staining in <10% of the tumor with weak intensity) was noted in 14 tumors: 5 for the MLH1 antibody, 1 for MSH2, and 8 for MSH6. One of the 5 MLH1 cases exhibited MSI and had an MLH1 germline mutation. Five of the 8 MSH6 cases exhibited MSI and had MSH2 germline mutations. In conclusion, our study shows that 1) IHC identifies a significant portion of colorectal tumors derived from MMR gene germline mutation carriers and can be used as an adjunct measure in the identification of HNPCC families, but IHC cannot replace MSI testing; 2) adenomas have similar MMR protein expression patterns as carcinomas and may serve as an adequate sample for screening purposes in the identification of patients with MMR mutations; 3) not all IHC-positive cases show uniform positivity throughout the tumor; and 4) weak and focal staining of an MMR protein may be associated with MSI or gene mutation or both, suggesting the need to incorporate staining intensity in further IHC studies.

Value of histopathology in predicting microsatellite instability in hereditary nonpolyposis colorectal cancer and sporadic colorectal cancer

Identification of colorectal carcinomas with high levels of DNA microsatellite instability (MSI-H) is important because of the suggested prognostic and therapeutic significance associated with MSI. The role of histology in identifying MSI-H colorectal carcinomas has been suggested by some studies but not confirmed by others. Furthermore, previous studies assumed that hereditary nonpolyposis colorectal cancer (HNPCC)-associated MSI-H tumors and sporadic MSI-H tumors have similar histology. This assumption, however, has been challenged by more recent studies. In this report, we first analyzed the value of various histologic features in predicting MSI-H in a series of 218 colorectal carcinomas containing mixed HNPCC and sporadic cases [77 tumors (35%) were MSI-H by polymerase chain reaction (PCR) method]. Then, we evaluated the various histologic features comparatively in two groups extracted from the 218 cases. Group A was composed of 84 tumors from 82 patients obtained based on a strong family history (HNPCC/HNPCC-like group) (male to female ratio, 42:40; age range, 23-80 years, median, 53.5 years). Thirty-one of the 84 tumors (41.7%) were MSI-H by PCR, and all 31 cases were HNPCC by Amsterdam criteria. Group B was composed of 109 patients with no family history of colorectal cancer or HNPCC-associated cancer, obtained from surgical clinics (sporadic group) (male to female ratio, 65:69; age range, 31-84 years, median, 65 years). Thirty-five of the 109 tumors (32.1%) were MSI-H by PCR. Our results showed that, overall, poor tumor differentiation, medullary type, mucinous type, signet-ring cell component, histologic heterogeneity, and increased tumor-infiltrating lymphocytes (TILs) were features more commonly seen in MSI-H tumors than in non-MSI-H tumors. Comparative analyses showed that the overall TIL count was significantly higher in HNPCC/HNPCC-like group, and mucinous type appeared to be more frequent in HNPCC MSI-H tumors than in sporadic MSI-H tumors. However, there was no significant difference in the odds ratio for predicting MSI-H status for any of the analyzed histologic features between HNPCC/HNPCC-like group and sporadic group, indicating that differences between HNPCC and sporadic MSI-H tumors did not significantly impact on the informative value of histology in predicting MSI in the two different clinical settings. TIL counts followed by histologic heterogeneity provided the greatest sensitivity and specificity in predicting MSI status in both HNPCC/HNPCC-like and sporadic cases. Using a stepwise logistic regression model, a formula was generated that could be used to calculate the probability of a colorectal carcinoma being MSI-H based on morphologic features.

MSH6 germline mutations are rare in colorectal cancer families

Germline mutations in MSH6 can cause HNPCC, which is associated with a tumor phenotype featuring MSI. However, tumors arising in persons with disease-causing mutations of MSH6 may or may not exhibit MSI. We used D-HPLC to screen for germline mutations in the promoter region, the coding region and the 3'-UTR of MSH6. Eighty-four families, enrolled on the basis of Amsterdam I and II criteria (HNPCC families) and less stringent criteria (HNPCC-like families), were tested for MMR gene mutations; 27 families had a disease-causing mutation in MLH1 or MSH2, and the remaining 57 families were tested for mutations in MSH6. Two protein-truncating mutations were identified in each of 2 families fulfilling the Amsterdam I criteria, being present in persons affected with early-onset colorectal cancers exhibiting MSI. Immunohistochemical analysis showed that expression of both MSH2 and MSH6 proteins was lost in the cancer cells of the 2 mutation carriers but only MSH6 protein expression was lost in 2 adenomatous polyps. A third possibly disease-causing mutation was found in a person affected with a tumor that did not exhibit MSI. In addition, we found 4 new polymorphisms and determined that neither of the 2 studied by association analysis conferred susceptibility to colorectal or endometrial cancer. Altogether, our results indicate that disease-causing germline mutations of MSH6 are rare in HNPCC and HNPCC-like families.