Occurrence of Spontaneous Tumors in the Central Nervous System (CNS) of F344 and SD Rats

Abstract

In order to accurately assess the carcinogenicity of chemicals with regard to rare tumors such as rat CNS tumors, sufficient information about spontaneous tumors are very important. This paper presents the data on the type, incidence and detected age of CNS tumors in F344/DuCrlCrlj (a total of 1363 males and 1363 females) and Crl:CD(SD) rats (a total of 1650 males and 1705 females) collected from in-house background data-collection studies and control groups of carcinogenicity studies at our laboratory, together with those previously reported in F344 and SD rats. The present data on F344/DuCrlCrlj rats (F344 rats) and Crl:CD(SD) rats (SD rats) clarified the following. (1) The incidences of all CNS tumors observed in F344 rats were less than 1%. (2) The incidences of malignant astrocytoma and granular cell tumor were higher in male SD rats than in female SD rats. (3) The incidences of astrocytoma and granular cell tumor were higher in SD rats than in F344 rats. (4) Among astrocytoma, oligodendroglioma and granular cell tumor, oligodendroglioma was detected at the youngest age, followed by astrocytoma, and ultimately, granular cell tumor developed in both strains. The incidences observed in our study were almost consistent with those previously reported in F344 and SD rats.

A Spontaneous Oligodendroglioma in the Lumbar Portion of the Spinal Cord in a Young BrlHan:WIST@Jcl (GALAS) Rat

“…They are an extremely rare central nervous system tumor in most strains of rat 3 . In Crl:CD(SD), F344/DuCrlCrlj, Wistar Hannover and F344 rats, the incidence of spontaneous oligodendroglioma is reported to be 0.1 to 0.4% in the brain and 0 to 0.1% in the spinal cord after about 32 weeks of age 4 , 5 , 6 , 7 . To our knowledge, there have been no reports regarding spontaneous oligodendroglioma in the spinal cord in young rats.…”

“…In neoplasms of the rat central nervous system, spontaneous astrocytoma occurs most commonly, followed by oligodendroglioma and granular cell tumor 12 . Spontaneous oligodendrogliomas are found principally in the cerebral hemisphere, and in a few cases, they have been reported in the rat spinal cord 1 , 2 , 3 , 4 . Oligodendroglioma generally occurs at a relatively advanced age: the youngest previously reported case was in the brain of a Crl:CD(SD) rat at 32 weeks of age 12 .…”

“…In conclusion, the tumor was diagnosed as an oligodendroglioma (low grade) based on its histological and immunohistochemical features. To our knowledge, there have been only a few reports on spontaneous oligodendroglioma in the spinal cord in Han:SPRD and Crl:CD(SD) rats 2 , 4 , and none have been reported in young rats or other rat strains. Therefore, our case is considered to be extremely rare and to be the first report in a young (9 weeks old) BrlHan:WIST@Jcl (GALAS) rat.…”