Spontaneous neoplasms in Wistar rats from a center for laboratory animal breeding of the Rio de Janeiro state, Brazil

The purpose of the present study was to check the prevalence and the pathologic features of spontaneous neoplasms found in Wistar rat, from the production colonies at the Center for Laboratory Animal Breeding, FIOCRUZ, Rio de Janeiro. One thousand nine hundred and sixty four Wistar rats were submitted to necropsy in the period between August 2002 and January 2007, after euthanasia in CO2 chamber. Tissue samples were collected, fixed in 10% buffered formalin and processed by the usual techniques for inclusion in paraffin. Thirty eight neoplasms were diagnoses and 36 rats had tumors, representing a prevalence of 1.8%. Among the 36 animals, only six (16.7%) were male and one (2.8%) young. The neoplasms were diagnosed with the following occurrences: mammary carcinoma (42.1%), mammary fibroadenoma (13.2%), hemangiosarcoma (7.9%), adenoma of the pituitary gland (7.9%), mammary adenoma (5.3%), fibrosarcoma (5.3%), primary papillary pulmonary adenocarcinoma (2.6%), sebaceous epithelioma (2.6%), ganglioneuroblastoma in the adrenal gland (2.6%), leiomyoma of the uterus (2.6%), mesothelioma (2.6%), osteosarcoma osteoblastic (2.6%), papilloma (2.6%). In this study the prevalence of spontaneous neoplasms was lower than the ones found in similar studies and the malignant tumors predominated. The sebaceous epithelioma and also the mucinous and simple papillary-cystic mammary carcinomas with spontaneous occurrence were described in Wistar rats for the first time.

laboratory animal; oncology; pathology; prevalence; Rattus norvegicus

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