Grading of tumors located in the tubular digestive tract is an integral component of pathology assessment reports but is subordinate to the histological typing of tumors with respect to the prognostic significance. Tumor grading has not been shown to be an independent prognostic marker for most tumor entities in the gastrointestinal tract; however, it may be relevant for further routine treatment decision making in early Union Internationale Contre le Cancer (UICC) stage cancers in which the prognosis for patients is less dominated by advanced tumor spread. Owing to the more favorable prognosis of microsatellite instability in colorectal cancer, the World Health Organization (WHO) has recommended that poorly differentiated tumors should be tested and graded as low grade (G1/G2) when microsatellite instability is detected. This recommendation has been integrated into the German S3 guidelines for colorectal cancers. Accordingly, microsatellite instability testing for grading purposes should become routine practice.
Keywords: Decision aid; Microsatellite instability; Prognosis; Therapy; Tumor typing.