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The title of the 2017 Society of Toxicologic Pathology symposium was “Musculoskeletal System.” A brief overview of the General Scientific Symposium is presented herein and describes the topics presented by each speaker. Symposium speakers addressed subjects pertinent to musculoskeletal system toxicologic pathology and drug development ranging from molecular biology of bone homeostasis to regulatory agency requirements and considerations for registration of bone therapeutics. This overview serves to summarize sessions and is intended as a guide to the individual submissions by speakers and symposium contributors. [ABSTRACT FROM AUTHOR]

The 2013 annual National Toxicology Program (NTP) Satellite Symposium, entitled “Pathology Potpourri,” was held in Portland, Oregon, in advance of the Society of Toxicologic Pathology’s 32nd annual meeting. The goal of the NTP Symposium is to present current diagnostic pathology or nomenclature issues to the toxicologic pathology community. This article presents summaries of the speakers’ presentations, including diagnostic or nomenclature issues that were presented, along with select images that were used for audience voting and discussion. Some lesions and topics covered during the symposium included a caudal tail vertebra duplication in mice; nephroblastematosis in rats; ectopic C cell tumor in a hamster; granular cell aggregates/tumor in the uterus of a hamster; Pneumocystis carinii in the lung of a rat; iatrogenic chronic inflammation in the lungs of control rats; hepatoblastoma arising within an adenoma in a mouse; humoral hypercalcemia of benignancy in a transgenic mouse; acetaminophen-induced hepatotoxicity in rats; electron microscopy images of iatrogenic intraerythrocytic inclusions in transgenic mice; questionable hepatocellular degeneration/cell death/artifact in rats; atypical endometrial hyperplasia in rats; malignant mixed Müllerian tumors/carcinosarcomas in rats; differential diagnoses of proliferative lesions of the intestine of rodents; and finally obstructive nephropathy caused by melamine poisoning in a rat. [ABSTRACT FROM AUTHOR]

To investigate the toxicity and carcinogenic potential of indole-3-carbinol (I3C), the National Toxicology Program has conducted 13-week subchronic studies in Fisher 344 rats and B6C3F1 mice, and chronic 2-year bioassays in Sprague-Dawley rats and B6C3F1 mice. While the chronic study results are not yet available, subchronic study results and short-term special evaluations of interim sacrifices in the 2-year rat bioassay are presented. F344 rats were orally gavaged ≤300 mg I3C/kg body weight 5 days a week for 13 weeks. Rats treated with ≥150 mg/kg demonstrated a dose-related dilation of lymphatics (lymphangiectasis) of the duodenum, jejunum, and mesenteric lymph nodes. Material within dilated lacteals stained positively for Oil Red O and Sudan Black, consistent with lipid. Electron microscopic evaluation confirmed extracellular lipid accumulation within the villar lamina propria, lacteals, and within villar macrophages. Analyses of hepatic and pulmonary CYP1A enzymes demonstrated dose-dependent I3C induction of CYP1A1 and 1A2. B6C3F1 mice orally gavaged ≤250 mg I3C/kg body weight did not demonstrate histopathological changes; however, hepatic CYP induction was similar to that in rats. The histopathologic changes of intestinal lymphangiectasis and lipidosis in this study share similarities with intestinal lymphangiectasia as observed in humans and dogs. However, the resultant clinical spectrum of protein-losing enteropathy was not present. [ABSTRACT FROM PUBLISHER]

The 2012 annual National Toxicology Program (NTP) Satellite Symposium, entitled “Pathology Potpourri,” was held in Boston in advance of the Society of Toxicologic Pathology's 31st annual meeting. The goal of the NTP Symposium is to present current diagnostic pathology or nomenclature issues to the toxicologic pathology community. This article presents summaries of the speakers’ presentations, including diagnostic or nomenclature issues that were presented, along with select images that were used for audience voting or discussion. Some lesions and topics covered during the symposium include eosinophilic crystalline pneumonia in a transgenic mouse model; differentiating adrenal cortical cystic degeneration from adenoma; atypical eosinophilic foci of altered hepatocytes; differentiating cardiac schwannoma from cardiomyopathy; diagnosis of cardiac papillary muscle lesions; intrahepatocytic erythrocytes and venous subendothelial hepatocytes; lesions in Rathke’s cleft and pars distalis; pernicious anemia and megaloblastic disorders; embryonic neuroepithelial dysplasia, holoprosencephaly and exencephaly; and INHAND nomenclature for select cardiovascular lesions. [ABSTRACT FROM PUBLISHER]

The heart is increasingly recognized as a target for toxicity. As studies in laboratory rodents are commonly used to investigate the potential toxicity of various agents, the identification and characterization of lesions of cardiotoxicity is of utmost importance. Although morphologic criteria have been established for degenerative myocardial lesions in rats and mice, differentiation of spontaneously occurring lesions from toxin-induced or toxin-related lesions remains difficult. A retrospective light microscopic evaluation was performed on the hearts of F344 rats and B6C3F1 mice from National Toxicology Program (NTP) studies of six chemicals identified in the NTP database in which treatment-induced myocardial toxicity was present. Two previously defined myocardial lesions were observed: “cardiomyopathy” that occurred spontaneously or as a treatment-related effect and “myocardial degeneration” that occurred as a treatment-related effect. Both lesions consisted of the same basic elements, beginning with myofiber degeneration and necrosis, with varying amounts of inflammation, interstitial cell proliferation, and eventual fibrosis. This observation is indicative of the heart’s limited repertoire of responses to myocardial injury, regardless of the nature of the inciting agent. A prominent differentiating factor between spontaneous and treatment-induced lesions was distribution and lesion onset. Once the respective lesions had undergone fibrosis, however, they generally appeared morphologically indistinguishable. [ABSTRACT FROM PUBLISHER]

This article describes the results of comparisons of digitally scanned whole slide images (WSIs) and glass microscope slides for diagnosis of tissues under peer review by the National Toxicology Program. Findings in this article were developed as a result of the data collected from 6 pathology working groups (PWGs), 1 pathology peer review, and survey comments from over 25 participating pathologists. For each PWG, 6–14 pathologists examined 10–143 tissues per study from 6- and 9-month perinatal studies and 2-year carcinogenicity studies. Overall it was found that evaluation of WSIs is generally equivalent to using glass slides. Concordance of PWG consensus diagnoses based upon review of WSIs versus glass slides ranged from 74% to 100% (median 86%). The intra- and interobserver diagnostic variation did not appear to influence the conclusions of any study. Based upon user opinions collected from surveys, WSIs may be less optimal than glass slides for evaluation of subtle lesions, large complex lesions, small lesions in a large section of tissue, and foci of altered hepatocytes. These results indicate that, although there may be some limitations, the use of WSIs can effectively accomplish the objectives of a conventional glass slide review and definitely serves as a useful adjunct to the conduct of PWGs. [ABSTRACT FROM AUTHOR]