Alys Bradley

Incidences and Range of Spontaneous Findings in Control Cynomolgus Monkeys (Macaca fascicularis) Used in Toxicity Studies

The authors performed a retrospective study to determine the incidences and range of spontaneous pathology findings in control cynomolgus monkeys. Data were collected from 570 monkeys (285 animals per sex), aged twelve to thirty-six months, from sixty regulatory studies evaluated at our laboratory between 2003 and 2009. The most common finding overall was lymphoplasmacytic infiltrates observed in the following incidence: liver (60.7%), kidneys (28.8%), heart (25.8%), salivary glands (21.2%), and stomach (12.1%). Inflammation also commonly occurred in the heart, kidneys, lungs, and stomach. The most common degenerative changes were localized fatty change in the liver, myocardial degeneration, and mineralization and pigment deposits in various tissues. Parathyroid, thyroid, and pituitary cysts; ectopic thymus in the parathyroid or thyroid gland; accessory spleen within the pancreas; and adrenohepatic fusion were among the most common congenital findings. Some incidental findings bearing similarities to drug-induced lesions were also encountered in various organs. It is hoped that the results presented here and elsewhere could form the groundwork for the creation of a reliable database of incidental pathology findings in laboratory nonhuman primates.

International Harmonization of Toxicologic Pathology Nomenclature: An Overview and Review of Basic Principles

The International Harmonization of Nomenclature and Diagnostic Criteria for Lesions in Rats and Mice is a global project that is publishing criteria for both proliferative and nonproliferative changes in laboratory animals. This paper presents a set of general suggestions for terminology across systems. These suggestions include the use of diagnostic versus descriptive terms, modifiers, combination terms, and grading systems; and the use of thresholds, synonyms, and terminology for some processes that are common to several organ systems. The purpose of this paper is to help the reader understand some of the basic principles underlying the International Harmonization of Nomenclature and Diagnostic Criteria for Lesions in Rats and Mice process.

STP Position Paper Recommended Practices for Sampling and Processing the Nervous System (Brain, Spinal Cord, Nerve, and Eye) during Nonclinical General Toxicity Studies

The Society of Toxicologic Pathology charged a Nervous System Sampling Working Group with devising recommended practices to routinely screen the central nervous system (CNS) and peripheral nervous system (PNS) in Good Laboratory Practice–type nonclinical general toxicity studies. Brains should be weighed and trimmed similarly for all animals in a study. Certain structures should be sampled regularly: caudate/putamen, cerebellum, cerebral cortex, choroid plexus, eye (with optic nerve), hippocampus, hypothalamus, medulla oblongata, midbrain, nerve, olfactory bulb (rodents only), pons, spinal cord, and thalamus. Brain regions may be sampled bilaterally in rodents using 6 to 7 coronal sections, and unilaterally in nonrodents with 6 to 7 coronal hemisections. Spinal cord and nerves should be examined in transverse and longitudinal (or oblique) orientations. Most Working Group members considered immersion fixation in formalin (for CNS or PNS) or a solution containing acetic acid (for eye), paraffin embedding, and initial evaluation limited to hematoxylin and eosin (H&E)-stained sections to be acceptable for routine microscopic evaluation during general toxicity studies; other neurohistological methods may be undertaken if needed to better characterize H&E findings. Initial microscopic analyses should be qualitative and done with foreknowledge of treatments and doses (i.e., “unblinded”). The pathology report should clearly communicate structures that were assessed and methodological details. Since neuropathologic assessment is only one aspect of general toxicity studies, institutions should retain flexibility in customizing their sampling, processing, analytical, and reporting procedures as long as major neural targets are evaluated systematically.

Proliferative and Nonproliferative Lesions of the Rat and Mouse Central and Peripheral Nervous Systems

Harmonization of diagnostic nomenclature used in the pathology analysis of tissues from rodent toxicity studies will enhance the comparability and consistency of data sets from different laboratories worldwide. The INHAND Project (International Harmonization of Nomenclature and Diagnostic Criteria for Lesions in Rats and Mice) is a joint initiative of four major societies of toxicologic pathology to develop a globally recognized nomenclature for proliferative and nonproliferative lesions in rodents. This article recommends standardized terms for classifying changes observed in tissues of the mouse and rat central (CNS) and peripheral (PNS) nervous systems. Sources of material include academic, government, and industrial histopathology databases from around the world. Covered lesions include frequent, spontaneous, and aging-related changes as well as principal toxicant-induced findings. Common artifacts that might be confused with genuine lesions are also illustrated. The neural nomenclature presented in this document is also available electronically on the Internet at the goRENI website (http://www.goreni.org/).

Spontaneous Lesions of the Cardiovascular System in Purpose-Bred Laboratory Nonhuman Primates

This retrospective study was performed to determine the range, occurrence and incidence of spontaneously arising histopathological findings of the cardiovascular system in purpose-bred laboratory nonhuman primates. Data were collected from 84 controlled toxicological studies with equal numbers of male and female animals and full tissue lists. Attempts were also made to standardize pathological terms used by various original pathologists. Tissue sections from 2464 animals, which included 2050 cynomolgus monkeys (Macaca fascicularis), 284 common marmosets (Callithrix jacchus) and 130 rhesus monkeys (Macaca mulatta) were examined. The most common cardiac finding was focal myocardial inflammation, subcategorized as either “inflammatory cell infiltration” (339) or “focal myocarditis” (131). Other cardiac findings included mineralization (29), endocarditis (16), pericarditis (10), squamous cysts (6) and ectopic thyroid tissue (5). Perivasculitis/vasculitis in the kidney, lung, meninges, sciatic nerve, and other tissues (206) was the most common vascular lesion. Focal myocarditis was more common in male (60%) than female (40%) animals. Cardiac mineralization and extramedullary hematopoiesis were more common in marmosets than other species while ectopic thyroid tissue was present in marmosets and cynomolgus monkeys. To our knowledge, this is the first study to demonstrate the range and incidence of spontaneous cardiovascular lesions in laboratory nonhuman primates.

Proliferative and Non-Proliferative Lesions of the Rat and Mouse Integument

The INHAND (International Harmonization of Nomenclature and Diagnostic Criteria for Lesions in Rats and Mice) project is a joint initiative of the societies of toxicological pathology from Europe (ESTP), Great Britain (BSTP), Japan (JSTP) and North America (STP). Its aim is to develop an internationally-accepted nomenclature for proliferative and non-proliferative lesions in laboratory rodents. A widely accepted international harmonization of nomenclature in laboratory animals will decrease confusion among regulatory and scientific research organizations in different countries and will provide a common language to increase and enrich international exchanges of information among toxicologists and pathologists. The purpose of this publication is to provide a standardized nomenclature for classifying microscopical lesions observed in the integument of laboratory rats and mice. Example colour images are provided for most lesions. The standardized nomenclature presented in this document and additional colour images are also available electronically at http://www.goreni.org. The nomenclature presented herein is based on histopathology databases from government, academia, and industrial laboratories throughout the world, and covers lesions that develop spontaneously as well as those induced by exposure to various test materials. (DOI: 10.1293/tox.26.27S; J Toxicol Pathol 2013; 26: 27S–57S)

International recommendations for training future toxicologic pathologists participating in regulatory-type, nonclinical toxicity studies.

The International Federation of Societies of Toxicologic Pathologists (IFSTP) proposes a common global framework for training future toxicologic pathologists who will support regulatory-type, nonclinical toxicology studies. Optimally, trainees should undertake a scientific curriculum of at least five years at an accredited institution leading to a clinical degree (veterinary medicine or medicine). Trainees should then obtain four or more years of intensive pathology practice during a residency and/or on-the-job “apprenticeship,” at least two years of which must be focused on regulatory-type toxicologic pathology topics. Possession of a recognized pathology qualification (i.e., certification) is highly recommended. A nonclinical pathway (e.g., a graduate degree in medical biology or pathology) may be possible if medically trained pathologists are scarce, but this option is not optimal. Regular, lifelong continuing education (peer review of nonclinical studies, professional meetings, reading, short courses) will be necessary to maintain and enhance one’s understanding of current toxicologic pathology knowledge, skills, and tools. This framework should provide a rigorous yet flexible way to reliably train future toxicologic pathologists to generate, interpret, integrate, and communicate data in regulatory-type, nonclinical toxicology studies.

Compilation of International Regulatory Guidance Documents for Neuropathology Assessment During Nonclinical General Toxicity and Specialized Neurotoxicity Studies

Neuropathology analyses as end points during nonclinical efficacy and toxicity studies are challenging and require trained personnel and particular equipment to achieve optimal results. Accordingly, many regulatory agencies have produced explicit guidelines for designing and performing neuropathology assessments for nonclinical studies. This compilation of international regulatory guidance for toxicologic neuropathology end points represents a set of criteria recommended for general toxicity studies and specialized neurotoxicity studies that should facilitate the efforts of individuals who plan, perform, analyze, and report neuropathology evaluations in nonclinical toxicity studies.

International Recommendations for Training Future Toxicologic Pathologists Participating in Regulatory-Type, Nonclinical Toxicity Studies

The International Federation of Societies of Toxicologic Pathologists (IFSTP) proposes a common global framework for training future toxicologic pathologists who will support regulatory-type nonclinical toxicology studies. Trainees optimally should undertake a scientific curriculum of at least 5 years at an accredited institution leading to a clinical degree (veterinary medicine or medicine). Trainees should then obtain 4 or more years of intensive pathology practice during a residency and/or on-the-job “apprenticeship,” at least 2 years of which must be focused on regulatory-type toxicologic pathology topics. Possession of a recognized pathology qualification (i.e., certification) is highly recommended. A non-clinical pathway (e.g., a graduate degree in medical biology or pathology) may be possible if medically trained pathologists are scarce, but this option is not optimal. Regular, lifelong continuing education (peer review of nonclinical studies, professional meetings, reading, short courses) will be necessary to maintain and enhance one’s understanding of current toxicologic pathology knowledge, skills, and tools. This framework should provide a rigorous yet flexible way to reliably train future toxicologic pathologists to generate, interpret, integrate, and communicate data in regulatory-type, nonclinical toxicology studies.

The International Nomenclature Project: An Update

One of the challenges for toxicologic pathologists is to translate the diverse range of morphologic changes that are observed in toxicity studies into a consistent and readily understood set of diagnostic terms to be tabulated and summarized in regulatory reports or peer-reviewed publications. Historically, there have been multiple efforts to provide uniform nomenclature for lesions observed in laboratory animals. These efforts began as early as 1973 and have culminated in various textbooks, workshop reports, and monographs. The efforts have typically focused on the rat and mouse and, in many cases, were limited to proliferative lesions. Many of the texts or documents that describe suggested nomenclature are either not widely available or are out of print. To address this issue, members of the major societies of toxicologic pathology (JSTP, BSTP, ESTP, and STP) have been engaged in an international collaborative effort to codify and publish uniform nomenclature for both proliferative and nonproliferative lesions in laboratory rodents. Several features unique to this effort include (1) a truly international scope, (2) implementation of an open comment period allowing a wide group of toxicologic pathologists the opportunity to provide input, and (3) availability in a Web-based format. The project goes under the acronym INHAND (International Harmonization of Nomenclature and Diagnostic Criteria for Lesions in Rats and Mice). Project oversight is provided by the Global Editorial and Steering Committee (GESC), which consists of members from each of the major societies of toxicologic pathology. The most important components of the INHAND project are the Organ System Working Groups. Formation of these groups is coordinated by the GESC, and they consist of a global chairperson and members from each of the major societies of toxicologic pathology. The GESC actively seeks out organ system experts to serve on these groups. In addition, the GESC often accommodates requests from pathologists who volunteer for a specific organ working group. The Organ System Working Groups have the responsibility to prepare the nomenclature guidelines for both proliferative and nonproliferative lesions of rats and mice for their assigned organ system. In addition to lesions that occur spontaneously, the groups are asked to determine if there are common, xenobiotic-induced lesions for which standardized nomenclature might be needed. The working groups draw heavily from existing nomenclature documents, Web sites, and publications including prior work of the Registry of Industrial Toxicology Animal-Data (RITA) and the Standardized System of Nomenclature and Diagnostic Criteria (SSNDC). For each diagnostic entity, the working group selects a preferred diagnosis and acceptable alternative diagnoses, provides diagnostic criteria and differential diagnosis, and prepares representative photomicrographs. An important feature of the INHAND project is the access provided to the global open Registry Nomenclature Information System (goRENI; www.goreni.org) (Figure 1). Access is provided to all members of toxicologic pathology societies worldwide. Access is free but must be requested through the goRENI Web site (Figure 2). Once access is granted, pathologists can navigate by organ systems (Figure 3) and ultimately select a diagnosis they would like to view. Within the goRENI system, each diagnostic entity is referred to as a ‘‘manuscript.’’ An example is the written information, and photographic illustrations, provided for a bronchiolo-alveolar carcinoma as shown in Figure 4. Once an organ working group has prepared a draft document, the nomenclature is placed on the goRENI Web site for review and discussion. Members of the contributing STPs are notified of the dates of the review period through their respective societies. Following the designated comment period, the working group revises the nomenclature documents and, in consultation with the GESC, finalizes the nomenclature for that organ system. Finalized nomenclature will be available to toxicologic pathologists in two forms: (1) electronic access via the goRENI Web site and (2) print-based publication in the toxicologic pathology journals. Due to the substantial costs associated with print-based This is an opinion article submitted to the Regulatory Forum and does not constitute an official position of the Society of Toxicologic Pathology or the journal Toxicologic Pathology. The views expressed in this article are those of the authors and do not necessarily represent the policies, positions, or opinions of their respective agencies and organizations. Conflict of interest: The authors have not declared any conflict of interest.