<bold>The aim of the study</bold> was to assess the frequency of hereditary nonpolyposus colorectal cancer in the Lower Silesia area.
<bold>Material and methods.</bold> The study population consists of 318 patients hospitalized between 2001-2002 on 14 surgical wards in the Lower Silesia area. Patients formed four groups: hereditary nonpolyposis colorectal cancer (HNPCC), suspected HNPCC (S-HNPCC), familial colorectal cancer (FCC) and cancer familial aggregation (CFA). The epidemiological data were analyzed (age on onset, gender, localization, extracolonic tumors in family).
<bold>Results.</bold> 3.77% of all patients with colorectal cancer (CRC) were diagnosed with HNPCC and 6.92% with S-HNPCC. The mean age of CRC onset in HNPCC group was 53.07; in the S-HNPCC group, 62.2. Seven male and 5 female patients were diagnosed with HNPCC; for S-HNPCC, 14 males and 8 females were diagnosed. In the HNPCC group, 55.55% of CRC were situated in the right colon and in 44.55%, the left colon. In the S-HNPCC group, 28.57% CRC was in the right colon and in 71.43%, the left colon. In the HNPCC and S-HNPCC groups, there were 4 patients diagnosed with synchronous sigmoid and rectal adenomas. Two of them were diagnosed during intraoperative colonoscopy. One patient was diagnosed with 3 metachronous lesions. In the families of 6 patients with HNPCC extracolonic tumors were identified.
<bold>Conclusions.</bold> 1. Knowledge of HNPCC criteria ensures proper treatment of the patient and their family. 2. During colonoscopy, the whole colon should be inspected. 3. Patients suspected of HNPCC should undergo intraoperative colonoscopy.