Nomenclature: Terminology for Morphologic Alterations

Most terms used in pathology are primarily derived from classical Greek and secondarily from Latin roots. Using these roots, the approach to making a diagnosis is hierarchical and permits much flexibility and complexity in the range of diagnostic terminology used. The disease process includes morphological terms, which are used to describe the major pathological processes or abnormalities occurring in an organ or a tissue. Qualifiers specify distribution, duration, character, and severity and are applied in conjunction with morphologies to further define or characterize the abnormalities. Since diagnostic pathology addresses individual or small groups of animals, there is typically more flexibility in defining and naming the disease process in each case. Rodent toxicity and carcinogenicity studies, on the other hand, have complex designs and incorporate large numbers of animals. They require statistical comparisons among treatment groups; hence, standardized nomenclature is necessary to make these comparisons possible. Microscopic examination of the tissues is often the most time-consuming phase of such studies. During this lengthy process, several factors can directly influence the diagnostic terminology, and consequently the quality of the pathology data.