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HNPCC patients had lower stage disease at diagnosis than the unselected CRC cases, mainly due to rarer distant metastases at diagnosis. They survived longer than unselected CRC patients with tumors of the same stage. The estimated death rate for the HNPCC cases, adjusted for stage and age differences, was at most two-thirds of the rate for the hospital series.

The presence of rectal cancer should not preclude the diagnosis of HNPCC, because the incidence of rectal cancer in MSH2 was comparable with that in the general population. Phenotypic variations, including the preponderance of extracolonic cancers in MSH2 patients, did not result in survival differences between genotypic subgroups. These phenotypic features of HNPCC genotypes may have clinical significance in the design of specific screening, surveillance, and follow-up for affected individuals.

HNPCC patients had lower stage disease at diagnosis than the unselected CRC cases, mainly due to rarer distant metastases at diagnosis. They survived longer than unselected CRC patients with tumors of the same stage. The estimated death rate for the HNPCC cases, adjusted for stage and age differences, was at most two-thirds of the rate for the hospital series.

Although nonspecific, decreased resting and squeeze pressures were found in 90 percent of patients with anal sphincter injury. Decreased anal sphincter length or vector symmetry index were present in only 42 percent of patients with known sphincter injury. When limited to the distal 1.5 cm of the anal canal, transanal ultrasound identified all known sphincter injuries but falsely identified injury in 10 percent of women with intact anal sphincters. Transanal ultrasound in combination with decreased anal pressures correctly identified all intact sphincters and 90 percent of known anal sphincter injuries.

Transrectal ultrasound is an accurate modality for selecting patients for neoadjuvant treatment. Preoperative chemoradiation produced downstaging in 56 percent of patients. Factors related to early recurrence included residual nodal disease and failure to downstage T after neoadjuvant chemoradiation.

Poor differentiation and Crohn's-like reaction are more common in hereditary nonpolyposis colorectal cancer than colorectal cancers from general population. Poor differentiation and lymph node metastases are more commonly seen in MSH2-associated cancers than MLH1. Evaluation of the natural history, pathogenesis, and prognosis of colorectal cancer in hereditary nonpolyposis colorectal cancer should include consideration of which mismatch repair genes are mutated and what the specific mutations are.

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