OBJECTIVETo compare the accuracy of preoperative assessment in differentiation and grading of rectal adenocarcinoma.

METHODSOne hundred consecutive patients diagnosed as invasive rectal cancer by colonoscopy biopsy and undergone operation in the Changhai Hospital from March 2006 to May 2008 were studied retrospectively. Patient characteristics, examination records, operative and pathologic reports were reviewed. The slides of preoperative biopsy and postoperative pathologic specimen were reviewed to identify the differentiation by a single pathologist. The results of preoperative biopsy were compared to those of postoperative specimen which was considered as final diagnosis. The accuracy of preoperative assessment of differentiation was calculated. Patients were then divided into two groups based on the preoperative differentiation:the low-grade tumor including well and moderately differentiated tumors, and the high-grade tumor consisting of poorly differentiated and undifferentiated tumors. The accuracy of grading was also calculated.

RESULTSThe accuracy of preoperative assessment of differentiation was 72%, with 20% overgrading and 8% undergrading, while the accuracy of preoperative grading was 91%, with 4% overgrading and 5% undergrading. The accuracy of grading was significantly higher than that of specific differentiation(P<0.01).

CONCLUSIONThe grading of preoperative biopsy has high accuracy rate and should be considered in clinical practice.