National Toxicology Program nomenclature for hepatoproliferative lesions of rats

The manuscript describes deliberations and decisions amved at by a panel of experienced toxicologic pathologists, attempting to deal with a continuing problem in the safety (or risk) evaluation of drugs and chemicals using one strain ofrat. The major and significant suggested change is to replace the term neoplastic nodule with hepatocelliilar hyperplasia and hepatocellirlar adenonla, and then to re-evaluate the results and implications of shifting back to more conventional diagnostic terms. This is a rational and commendable move on the part of the NTP and reflects a reality of group efforts to exercise common sense, act responsibly, and provide leadership in critical issues. I agreed with the spirit (a modicum of diagnostic uniformity) of the Squire-Levitt recommendations of 1975 but not the imposition of a new, misunderstood term, neoplasric nodule which essentially left the less decisive diagnostic pathologist off the hook. If not convinced, call it neoplastic nodule, rather than hyperplastic nodule, and the diagnosis would not likely be challenged by reviewing panels. This allowance for lack of confidence and self-discipline has permitted some potentially useful drugs and chemicals to be unfairly categorized as carcinogens, sometimes to be reassigned by a more discerning group of pathologists at a later review. I have not agreed with the “neoplastic nodule ” concept and therefore have never recognized or used it