Comparative Incidences and Biological Outcomes for Thymoma in Various Rat Strains in National Toxicology Program Studies

Thymomas from 277 Fischer 344/N (F344/N), 10 Sprague Dawley (HSD:Sprague Dawley SD) (SD), 129 Wistar Han [Crl:WI(Han)] (WH), and 4 Wistar Outbred (WO) rats were reviewed from long-term studies in the National Toxicology Program (NTP) database. The incidence of thymomas in F344/N rats was slightly hi...

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Bibliographic Details
Published in:Toxicologic pathology 2019-10, Vol.47 (7), p.833-841
Main Authors: Moore, Rebecca R., Nagai, Hiroaki, Miller, Rodney A., Hardisty, Jerry F., Allison, Neil, Shockley, Keith R., Malarkey, David E.
Format: Article
Language:English
Subjects:
Animals
Female
Incidence
Male
Rats
Rats, Inbred F344
Rats, Sprague-Dawley
Rats, Wistar
Rodent Diseases - epidemiology
Thymoma - epidemiology
Thymoma - veterinary
Thymus Neoplasms - epidemiology
Thymus Neoplasms - veterinary
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Summary:Thymomas from 277 Fischer 344/N (F344/N), 10 Sprague Dawley (HSD:Sprague Dawley SD) (SD), 129 Wistar Han [Crl:WI(Han)] (WH), and 4 Wistar Outbred (WO) rats were reviewed from long-term studies in the National Toxicology Program (NTP) database. The incidence of thymomas in F344/N rats was slightly higher in males than in females, while the incidences in SD and WH rats were higher in females than in males. Only male WO rats were used in NTP studies. Of the 277 thymomas in F344/N rats, 235 (84.8%) were benign and 42 (15.2%) malignant, 14 of which exhibited metastasis. Of the 10 thymomas in SD rats, 5 (50%) were benign and 5 (50%) were malignant, one of which exhibited metastasis. Of the 129 thymomas in WH rats, 126 (98%) were benign and 3 (2%) were malignant, 1 with metastasis. Of the 4 thymomas in WO rats, 3 (75%) were benign and 1 (25%) was malignant, with no metastases. Malignant thymomas in F344/N and WH rats showed a propensity to be the cause of death and to result in early mortality, whereas the benign thymomas were associated less often with decreased survival. No occurrences of this neoplasm were reported to be related to exposure to any test articles.
ISSN:0192-6233
1533-1601
DOI:10.1177/0192623319863119