Biallelic MLH1 SNP cDNA expression or constitutional promoter methylation can hide genomic rearrangements causing Lynch syndrome

A positive family history, germline mutations in DNA mismatch repair genes, tumours with high microsatellite instability, and loss of mismatch repair protein expression are the hallmarks of hereditary non-polyposis colorectal cancer (Lynch syndrome). However, in ~10-15% of cases of suspected Lynch syndrome, no disease-causing mechanism can be detected

Endoscopic management of nonampullary duodenal polyps

Duodenal polyps are a rare finding in patients presenting for gastroscopy, being found in 0.3–4.6% of cases. The majority of patients are asymptomatic. The most common lesions necessitating removal are duodenal adenomas which should be differentiated from other mucosal lesions such as ectopic gastric mucosa, and submucosal lesions such as carcinoids and gastrointestinal stromal tumours (GISTs). Adenomas can occur sporadically or as part of a polyposis syndrome. Both groups carry malignant potential but this is higher in patients with a polyposis syndrome. The majority of sporadic duodenal adenomas are flat or sessile and occur in the second part of the duodenum. Historically duodenal adenomas have been managed by radical surgery, which carried significant mortality and morbidity, or more conservative local surgical excision which resulted in high local recurrence rates. There is growing evidence for the use of endoscopic mucosal resection (EMR) techniques for treatment of sporadic nonampullary duodenal adenomas, with good outcomes and low complication rates. Endoscopic submucosal dissection (ESD) carries greater risk of complications and should be reserved for experts in this technique. Patients with sporadic duodenal adenomas carry an increased risk of colonic neoplasia and should be offered colonoscopy. The impact of endoscopic resection on the course of polyposis syndromes such as familial adenomatous polyposis (FAP) needs further study