Establishing a diagnostic road map for MUTYH-associated polyposis

A case report of a patient with first phenotype of papillary thyroid carcinoma and heterochronous multiprimary tumor harboring germline MUTYH Arg19*/Gly286Glu mutations

MUTYH-associated polyposis (MAP) is an autosomal recessively inherited disease with multiple system tumors mainly in alimentary system. Tumor occurrence of MAP patients is highly heterogeneous in space and time. MAP is associated with germline biallelic mutations in MUTYH. The targeted next‑generation sequencing technology and Sanger sequencing are the important methods to screen MUTYH mutations now. Herein, we identified a patient with heterochronous multiprimary tumor carring MUYTH Arg19*/Gly286Glu compound heterozygous mutations. The patient in this case had a first phenotype of thyroid cancer at age 44, which earlier 2 years than the alimentary system cancers. In conclusion, our case report creases the in-depth understanding of the MAP heterogeneous phenotype and further reminds recommendations for improvement of health management and genetic counseling, special treatment plans.

Hereditary or sporadic polyposis syndromes

Polyposis syndromes are encountered in endoscopy practice, and are considered rare entities, accounting for ≤1% of colorectal cancer. Polyposis can occur within inherited syndromes or as "sporadic" cases of unknown etiology. Their proper characterization is relevant for patient management, and should nowadays drive appropriate genetic tests which have a key role in clinical practice for driving surveillance and colorectal cancer prevention, enlarged to relatives. Polyposis classification is based upon polyp number and histology, familial and personal history. This review will explore the polyposis nosology and their genetic determinants in the emerging scenario of Next Generation Sequencing which allow testing multiples genes in parallel. This capability will likely continue to increase the range of polyposis predisposing genes, contributing to define new clinical entities.

Somatic c.34G>T KRAS mutation: a new prescreening test for MUTYH-associated polyposis?

We investigated the somatic c.34G>T KRAS transversion as a marker suggestive of MUTYH-associated polyposis (MAP). We compared 86 adenomas and 19 colorectal cancers (CRCs) of 30 MAP patients to 135 adenomas and five CRCs of 47 familial adenomatous polyposis (FAP) patients. The c.34G>T mutation was investigated by DNA sequencing. Secondly, the germline MUTYH gene sequence was analyzed in patients carrying c.34G>T in CRCs diagnosed between 2008 and 2012. The c.34G>T was present in 39.7% of MAP adenomas versus 1.6% of FAP adenomas (P < 0.01). Sensitivity and specificity for detecting MAP were 39.7% and 98%, respectively. Sensitivity increased with the number of adenomas tested (P = 0.039). KRAS exon 2 analysis was performed on 2239 CRC and 2.2% harbored the c.34G>T transversion. Among 28 carriers of the c.34G>T mutation, biallelic MUTYH mutations were detected in seven patients (25%). One patient did not have any polyp or family history and did not fulfill criteria for MUTYH testing. With high specificity, the c.34G>T mutation seems to be a useful and promising test for MAP. For polyposis, it may guide genetic testing toward APC or MUTYH. If routinely performed in CRC patients, it could help to diagnose MUTYH-mutation carriers, even when they don't fulfill genetic testing criteria.

The molecular basis of rectal cancer

The majority of rectal carcinomas are sporadic in nature, and relevant testing for driver mutations to guide therapy is important. A thorough family history is necessary and helpful in elucidating a potential hereditary predilection for a patient's carcinoma. The adequate diagnosis of a heritable tendency toward colorectal carcinoma alters the management of a patient disease and permits the implementation of various surveillance algorithms as preventive measures.