A pathology report is written to convey information concerning the pathologic findings in a study. This type of report must be complete, accurate and communicate the relative importance of various findings in a study. The overall quality of the report is determined by three Quality Indicators: thoroughness, accuracy, and consistency. Thoroughness is the identification of every lesion present in a particular organ or tissue, including spontaneous background lesions. Experienced pathologists familiar with background lesions may disregard certain types of lesions or establish a threshold or a severity above which background lesions are diagnosed. Accuracy is the ability to make, and precisely communicate, correct diagnoses. Nomenclature of lesions is a matter of definition and experienced pathologists generally agree as to what terms are to be used. Consistency is the uniform use of a specific term to record a defined lesion and implies that the same diagnostic criteria are being followed for each type of diagnosis. The relative severity of nonneoplastic lesions can be recorded either semiquantitatively or quantitatively. Semiquantitative analysis involves the application of defined severity grades or ranges for specific lesions. Quantitative analysis (counts and measurements) can be performed manually or electronically, utilizing image analysis and stereological techniques to provide numerical values. When both qualitative and quantitative parameters are applied in preparation of a pathology report, the recorded pathology findings can be interpreted and put into perspective. The use of this approach assures a reader that the pathology report meets the highest standards.

The INHAND (International Harmonization of Nomenclature and Diagnostic Criteria for Lesions in Rats and Mice) project is a joint initiative of the Societies of Toxicologic Pathology from Europe (ESTP), Great Britain (BSTP), Japan (JSTP), and North America (STP) to develop an internationally accepted nomenclature and diagnostic criteria for nonproliferative and proliferative lesions in laboratory animals. The purpose of this publication is to provide a standardized nomenclature and diagnostic criteria for classifying lesions in the digestive system including the salivary glands and the exocrine pancreas of laboratory rats and mice. Most lesions are illustrated by color photomicrographs. The standardized nomenclature, the diagnostic criteria, and the photomicrographs are also available electronically on the Internet (http://www.goreni.org/). Sources of material included histopathology databases from government, academia, and industrial laboratories throughout the world. Content includes spontaneous and age related lesions as well as lesions induced by exposure to test items. Relevant infectious and parasitic lesions are included as well. A widely accepted and utilized international harmonization of nomenclature and diagnostic criteria for the digestive system will decrease misunderstandings among regulatory and scientific research organizations in different countries and provide a common language to increase and enrich international exchanges of information among toxicologists and pathologists.

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Naphthalene administered by inhalation at concentrations of 10, 30, or 60 ppm for 6 hours per day, 5 days per week for 105 weeks caused nonneoplastic and neoplastic effects in nasal respiratory and olfactory regions of male and female F344/N rats. Non-neoplastic nasal effects were characterized by an increase in the incidence and severity of a complex group of lesions, including atypical hyperplasia, atrophy, chronic inflammation, and hyaline degeneration of olfactory epithelium; hyperplasia, squamous metaplasia, hyaline degeneration, and goblet cell hyperplasia of the respiratory epithelium; and hyperplasia and squamous metaplasia of mucosal glands. Neoplastic effects were characterized by the induction of two types of rare primary nasal tumors, olfactory neuroblastomas and respiratory epithelial adenomas. The incidences of olfactory neuroblastomas in males at 0 ppm, 10 ppm, 30 ppm, and 60 ppm were, respectively, 0%, 0%, 8%, and 6%, whereas in females they were 0%, 4%, 6%, and 24%. The incidences of respiratory epithelial adenomas in males at 0 ppm, 10 ppm, 30 ppm, and 60 ppm were, respectively, 0%, 12%, 17%, and 31% and in females 0%, 0%, 8%, and 4%. The olfactory neuroblastomas and respiratory epithelial adenomas were considered carcinogenic effects related to naphthalene exposure based on their relatively high incidence in exposed rats, their absence in concurrent control rats and NTP historical controls, and their rare spontaneous occurrence in rats of any strain.